Leaf shows water stress, as in not enough getting to the top.
Determining just what is doing that is waht you need to figure out.

Suggestions:
If still hot, temporary shade might help.
Using your handy ever-present moisture meter -- a finger -- inserted into the soil and rootball is much more reliable than a meter device.
If planted from a container, make certain the rootball is moist because that's what dries out first.

Oh yes: a tip for next time you plant --
Don't mix organic matter into the planting hole. Either amend the entire area or use it as a mulch.

Also check for borer damage around the graft union; as Jean said, something is keeping water from getting to the leaves. Fuji tolerates 110F+ with ease, so something is wrong.

Try one of those 6' wide Bistro umbrellas mounted overtop your tree to protect it from the sun during the middle of the day .... in the mornings and evenings, the sun should still reach the tree.

This may help with the lack of moisture getting to the leaves, as I think it may be that the tree is overheating and the sun is evaporating the water in the leaves faster than the roots can pull it out of the ground.

Unfortunately, if this fixes your problem, it's just a temporary fix ... Your tree will be getting bigger. How tall will the tree be when it reaches maturity?

Looks like drowning injury to me- symptoms can be quite similar to too little water. Your area is not too hot for Fuji, the issue is more about are winters cold enough (to create full dormancy) so I think you can ignore the advice about providing shade. It often gets over 100 in the Sacramento Valley where I've seen commercial Fuji orchards.

I think you answered your own question when you mentioned drainage issues. If the majority of leaf area is injured you can expect the same is true of the functioning root system, so recovery will be very slow, at best, if this is the actual problem.

I was thinking the same as harvestman. I've been through it. Good chance the bagged soil is soaked up like a sponge. I don't like adding outside soil when planting a tree. If you want to mix in a little of your own composts, fine. But keep the percentage low. You can add your compost all you want in future years, spread it on top of the ground and let water take the nutrients down.

It will be hard to fix this if it is the case. The surrounding ground is going to be slow to wick it away. Shade it and remove mulch is the best chance.

On the subject of mixing fancy dirt with your home soil: your trees roots are going to reach beyond that hole pretty fast and the % of root contacting the fancy soil gets pretty small, therefor no advantage in the big picture. Disadvantage is this soft spot that fills with water when it rains and wants to sit there water logged, much like a pot above ground.

When you say you dug a big hole did you dig it deep or wide? If you dug it deep and put the root ball on top of loose soil it will settle and your tree will end up to deep.

A rule of thumb for me when I was by Sacramento was a 1 gallon pot root ball got planted 1-2" high. A 5 gallon root ball got planted 2-4" high. A 15 gallon root ball got planted 4-6" high. This seemed to accomodate the settling issue and the tree ended up at or above the exiting soil level.

Check your soil level on the tree and if it's too deep, lift it out of it's hole and add soil to bring it to a good level. The roots will not have grown much so it should be easy for you to do over.

Once a week should be sufficient water for now. It looks like over watering from your picture. Either from to frequent watering or from water standing in the hole from it being to deep.

You don't need to worry about the heat. The Central Valley near Sac got at least 10-15 days of summer heat. My Fuji's did just fine there in full sun.

Also you might take a look at the "lay of the land" around this tree. Is it in a spot where other water may be filtering down to it (at the bottom of a hill, or in a bowl). That too could be contributing to an over watering problem.

Other considerations are the type of soil which surrounds the hole you dug. If it is mostly clay, you may have created a large pot which the water can't get out of.

On the other hand, if after complete watering the soil remains soppy for more than a day, the problem is almost certainly drainage. overly deep planting can take quite a while to create issues and the graft union is a pretty good marker to see where this issue stands.

I've never seen an apple tree killed by planting it too deep and I've seen thousands of em that I didn't plant.

Putting compost in the planting hole was a mistake because it's causing the water to not drain. Hence the roots are drowning as Hman posted. At this time, it's too late to try to undo the damage by replanting the tree.
You'll probably have to replace the tree. Next time look at some videos on planting apple trees.

--"Leaf shows water stress, as in not enough getting to the top. "--

Curious if the soil is reading so soggy why it's having that issue. I wonder what else would stop it from being able to pull the water from the ground. I have a total of 5 trees planted pretty much the same way and all the others dry out in a few days to a week, and this one does not.

--"If still hot, temporary shade might help." --

Over the weekend I removed the red wood mulch entirely to see if that helps with the soil drainage, and did a mulching of pure compost in the basin and 1 foot around the bricks for now. Last week I also added a 30% shade sunblock cloth over the tree to hope to reduce the direct heat. So far no change.

--"Using your handy ever-present moisture meter -- a finger -- inserted into the soil and rootball is much more reliable than a meter device. "--

I did so and basically found, yet it's damp to moist. Pretty much a less accurate version of what I found by metering. not sure why that is more reliable.

--"Also check for borer damage around the graft union"--

Could you be a bit more specific on what I'm looking for an where; I'm a bit new to fruit trees and still figuring it out. Appreciate any additional info.

--"When you say you dug a big hole did you dig it deep or wide?'--

Mostly wide, the depth was about the same, maybe a little less than the root ball with about 2-3 feet out in every direction. Since the topsoil in the yard is basically exactly the same as a kid's sandbox - seems like it would need something a bit healthier to get started in.

I can take a look to see if it seems like it sunk: but you're saying it should be ok to pull and replant a bit higher if so?

--"Is it in a spot where other water may be filtering down to it (at the bottom of a hill, or in a bowl). Other considerations are the type of soil : If it is mostly clay, you may have created a large pot which the water can't get out of."

It's on the same level as the rest of the yard and honestly we've had like 0 inches of rain this year so the only water in the yard is what is being applied directly (no runoff to speak of).

The soil is sand, very very loose sand. I have a total of 5 trees planted pretty much the same way and all the others dry out in a few days to a week, and this one does not.

--"Putting compost in the planting hole was a mistake because it's causing the water to not drain."--

I'm interested in this as the compost had the exact same consistency of the bagged garden soil - so just curious why it would hold water- or are we saying it all will?

The compost along with the bagged garden soil is retaining the water and not allowing the roots to dry out.
Trees don't like wet roots. When planting a tree, you should refill the hole with the original soil, so the tree can get acclimated to its new home. As the compost breaks down, it's going to create air holes around the roots, which you don't want.

You said you planted it several months ago.

At this stage, the place to test the moisture content is the original rootball because the roots area still there and NOT yet into the surrounding area.