Good picture. This looks to me like Cotton Wool Disease, Flavobacterium Columnare (also known as Flexibacter Columnaris), which is not a fungal infection. It's caused by a number of factors: poor water quality, poor diet, sudden changes in water like temperature etc, low oxygen levels, and of course the ever-present word 'stress' which could include threats from other fish.
If that's what you're dealing with, it must be treated early for the strongest chance of not being fatal. As Aiken says, you have a lot of different medications going on; in other words, best to diagnose properly and narrow it down to the best choice. Armed with this name, there are pictures online to see if you find a match (look up Cotton Wool Disease, hit 'images') as well as treatment suggestions. Hopefully you'll get more advice here - especially if you provide more of the info Aiken asked for.
I also want to mention the apple snails. There's a lot of confusion about apple snails/mystery snails. It doesn't help that the official definition in most State's fish and game depts is that a mystery snail is classified as an apple snail but an apple snail is not a mystery snail. Huh? The most obvious way to tell is that apples are very big, mysteries are smaller. That doesn't help much, as every snail has to start small, and some mysteries can grow pretty big. If you bought your snails in a fish shop, especially a big-box store, it's probably a mystery. If you or a friend found on the side of the road, it's probably an apple. But apple snails can also be bought. Confused yet?
Why am I blathering on about this? Apple snails carry diseases that can infect an entire tank (that's why they're banned in many places). Mystery snails do not. If you have true apple snails in there, they may be the cause of disease. One quick eyeball way to tell the difference (no pun intended) is color: apple snails come in brown and a golden-brown. If your snails are blue, white, bright gold, or striped magenta, they are mysteries. But then again, mysteries also come in brown. Hope all this helps and doesn't confuse the issue.