[Matt Nace]

Texastech
..out of curiosity what size tank are they in? What fish are they??

White "dots" usually means ick....usually just one or two specs before it gets way worse.

Cotten-like is a fungus. This usually only affects stressed or injured fish.

Fin/tail rot, usually appears as frayed  or the fins look ragged, then gradually eroding away to nothing

I would say raise the temp slightly and if it looks like a wool , then get a fungus treatment. Maroxy or Maracyn have always worked for me, depending on what you have, and what fish it is affecting. Maracide for ick or use salt.