Correlation does not equal causation. Gills survive Ich really well as do most scale fish. Warm weather will speed up the life cycle of the parasite that causes Ich and it will tend to clear up going into summer.

Nope have not put char in my systems yet but it does seem like an easy way to charge it though I can see it taking up too much nutrient depending on how much you use at one time vs. the size of the system.