Hello Vaj.
You must have tall ceilings, starting off w/a 6'er.

You said you water once a week.

Do you first test soil to make sure it's dry? Not only top soil, but down to the bottom of pot? To test, insert a thin stick/stake deep inside soil. If the stick comes out muddy the bottom layer is still wet.

Do you know its pot size?

You said the soil was packed. With water, perhaps?

Did the person who advised you to water, see your plant and soil?

About pests. Do the patches move? Could be Scale or Mealy.

Do you have a picture to share?

If Scale, Insecticidal Oil or Fish Emulion, 'I use FE' should rid them.

If Mealy. Wiping insects off w/Rubbing Alcohol and cotton ball/Q-Tip is recommended.

The sticky substance is honeydew, secreted by the insect.

For now, it's important to rid the insects. After that's accomplished, perhaps placing your tree in fresh medium and a new, if needed larger pot. Toni

If your sticky substance is honeydew, which is what a lot of the typical "sucking" type pests excrete, you should beable to find the actual insects. You'll usually find them on the bottom side of the leaves, and in the tight joints where the leaf stems join the main stems. Be mindful that plants can excrete sap also, so glops of sticky stuff could be sap, and not honeydew. My Pachira does this, as well as a few other plants.

As for your plant's decline, I suspect a light or watering issues. Pachira likes bright light, and will shed leaves if put in low light conditions. Also, overwatering and underwatering are big culprits of leaves that go from yellow to brown to floor. If you're using peat based soil, like Miracle Grow, you must know that after 6 months, it begins to break down, eventually turning into a very poorly draining soupy mess. This leads to a poor root system, which leads to rot. The plant then can't take up enough moisture, giving signs of underwatering. The typical response is to water more, which rots the roots more, until your plant dies. It'd be helpful to know your light situation, watering scheme, type of soil, fertilizing plan, etc.

Joe

Thanks for your replies! It definitely needs repotting and more food - agree. It gets eastern sunlight, so I expected some leaf droppage. But not this! I can't see any bugs, though I search. I haven't enocuntered scale before, but is this scale: brown patches grow on the leaves, and drops of honeydew along underside of veins, especially the central leaf veins. (Can't figure out how to add a photo or I would!)

You'd beable to find the scale bugs. Do a search of "scale on plants" and you'll get plenty of pictures. Brown patches on leaves are nothing more than dead/dry spots, which can come from sucking insects, or watering issues. Like I said, it'd be no new thing if it was sap, and not honeydew from bugs.

Joe

Vaj...Are brown patches soft or hard bodied?

Did you try picking one of the patches off?
There's many Scale families. I believe all are secreters.

A photo would be helpful. Toni

Clear sap along the veins is typical for Pachira.
I believe the process is called guttation, and is a normal excretion of salts...

Josh

Someone please tell this person how to post an image.

To include a picture in a discussion, you first need to upload the pic to a photo-hosting site. There are many free ones, but I like imageshack because it allows remote linking (where the picture shows up in the message, not just a link to click.) Once you have uploaded your picture, you can copy the code and paste it here in a discussion. When you click preview, if you see the image, everyone else will too. Use the code for embedding HTML. If you want to do this, you can!