Those home soil test kits I have found to be not very accurate, so what you should do is contact your locla office of the Cornell Cooperative Extension Service about having a good, reliable soil test done.
Then dig in to your soil with these simple soil tests,
1) Soil test for organic matter. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains� too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

Here is a link that might be useful: Cornell CES

anyone ever notice that...annabelles tend to turn brown at the edges? too little rain, too much wind, they don't care...like the Jets, no matter what you do, the outcome is a forgone conclusion.

the point is, you have to know if the problem is soil or not. yeah, annabelles get mildly chlorotic rather easily, but they are also quite tolerant of it.

before you go about doing a lot of stuff, give the osmocote time to work. it's good stuff, but it doesn't work overnight. if you do six things, maybe you only had to do one. but which one?

I think I would go for a good soil test too. You started with mystery soil and added lots of bagged topsoil, which is arguably mystery soil also.

One thing that almost never hurts, though, is to add compost. :-D

"The guy at the nursery recommended Osmocote now, which I did, but that doesn't feel like enough. Does anyone more experienced have any recommendations for what I can do?"

I agree with him 100% Any particular reason you "feel" like it is not enough? :)

"Does anyone more experienced have any recommendations for what I can do?"
Yes I would suggest osmocote ;)

I like Vigaro slow release fertilizer 'tomato/plus calcium'. It has all needed micro and macronutrients.

Thanks, everyone. You're absolutely right--I had no reason to distrust him. I just felt he was busy and it seemed too easy! Anyway, I applied Osmocote, and I will wait patiently for spring and give it a chance to do its thing. I'll look into the soil and add some compost, too.
Thanks again!

Dont use too much!! Use it at even half stregth. So use half as much as it says on the lable!!!

Compost is more important then miracle grow.