Help my fish are all dying and I don't know why. My water levels are ph 7.2 Ammonia<0.25 and NO-2 =2 The tetras all seem to have Dots on them that look like air bubbles stuck to their tails. Our betta who is over 3 years old has a cotton like ball on his head. and my platy has a hole in her tail and it looks like scales are falling off of her side. Does anyone know what all of this means??????