Hey guys i've had my fish for about 4 months now and everything is going fine. Well except for today when i noticed one of my red wag tails was crashing at the bottom of the tank? I did some research online and i read that this meant that my fish was tired? The last time i cleaned the tank was about 2 weeks ago, i have a sand bottom (which gets dirty very quickly? how do i solve this?) everything else in the water is normal. Another one of my platies has a little bump/sore above it's tail and dorsal fin. It looks like an open wound filled with pus. Again, i only saw it today!! (I look at my fish everyday) What can this be? Has something suddenly gone wrong with my tank? All my other fish are doing fine. Any help would be greatly appreciated.