Tank Mate: Apple snail - Question

[Kokonoko]

I did have an Apple Snail ('mystery snail') in my 10g with my betta fish. Although, in the past two weeks the snail has become increasingly less active, staying mainly near the surface of the water. What concerns me more though is the waste it seems to be leaving behind. I'll have pictures of this up soon, but right now I have it isolated in a fresh 2g tank by itself with a little bit of aquarium salt in the bowl.

The waste contains 2 diffirent materials. One seems to be stool, being a brownish, lumpy substance. The other is a clear white goo that sticks to the glass where its been. Other symptoms include floating (Not abnormal by itself, but sometimes while floating it will slightly hang out of its shell <-- not a good sign in most cases), inactivity (little to no movements for long durations of time, sometimes a day or two) and a large cavity all around entrance of shell (which from what I've read, makes me think the mantle organ has collapsed !! )

Does anyone have some suggestions? I'll try to post some pictures up soon, once I place him back in the 10g aquarium.