I've had my mollies for a few weeks now and they're all doing fine, but now one had swim bladder issues and I cured him, then another has internal parasites and not eating (she's in a hospital tank right now) and now I have another molly with some white dot on it's tail fin. It doesn't look like ich but a kind of fungus? Need a 2nd opinon. Water parameters are fine. I just did a water change the day before yesterday and I have 4 mollies in a 20g tall.