How do you know what disease a fish has He has cluster of white bumps that now look like they are falling off another area was the same and it turned black another fish has one white bump on heand?

The first thing you need to do is start changing some water. The fish is being killed by ammonia because you are not changing its water often enough. The rules for keeping fish are :- 1 inch of fish needs a minimum of 1 gallon of water :- every tank needs a cycled filter:- every tank needs to have at least 50% of its water changed weekly. If you are not following those rules above, you are bound to fail in keeping fish healthy and alive for long.