i recently changed my heater because the old one quit working from a 300w to 450w and i noticed just recently that it looks like his skin right at the end near his mouth is like burned or deteriorating and also one of his smalled whiskers had the same issue and today the skin is peeled off the end so its just the bone or whatever he even had a small spot on his eye... my tank is clean the filtration is good and filters are clean i added stress coat in hopes it would help... he hasnt been eating normal and isnt as active as he usuallly is what could this be? and what can i do?