I bought a beautiful dieffenbachia full and dark green leaves. I took it to work and for some time it seemed to be thriving. After a while it started yellowing with soft almost soggy leaves. I took it home, dumped the soil out, added rocks to the bottom and perlite to the soil that was pretty wet. I put it under my sky light in my bedroom with my large leaf
Dieffenbachia that have been there for years and have thrived. After two weeks my plant continues to yellow. I've removed the yellow leaves but even the new growth is light green and appears like it will turn yellow too. I haven't watered because the soil as it appears very moist which is why I added the rocks and perlite. I'm disappointed and ready to put it in the garbage. Is there any hope for it?
You are on the right track. The roots are too wet. They need oxygen. Gently loosen the soil around the roots to let the air in. Give the plant a warm, dry, light, and low humidity place to dry out. You may need to give it dry soil if it still does not dry out fast enough. Continue to remove the yellow leaves, and continue to loosen the soil to let the air in. It may be good to spray it with an organic fungicide, like a SaferSoap product. Watch for rot around the base of the main stem. If you can save the roots and main stem, you may be able to revive it. If rot or fungus damage the roots or main stem it is garbage.
Plants roots need oxygen as much as they need moisture, but too much of either will kill them. So balance of the two is the most important thing to learn when it comes to keeping the soil healthy. It is even more so in the winter when the plant wants to go dormant and is not using very much of either. Add to that the shock of being a new plant in a new environment. Don't feel discouraged, it happens to all of us. Dieffenbachias are pretty tough plants, so it will probably be all right.
I don't recommend rocks in the pot. You can leave them for now, but when you pot it up, I would leave the rocks out. They can move around and block the drainage holes, fungus, and disease can form on them, they restrict the root growth so that they need to be potted up more often, among other things.