i left my fish in the care of my roomate over the long weekend, when i returned i had two dead balas and some of my oscars on one more bala have small white dots all over them. my dimpsys appear to be fine and so does my pacu. ive never seen this, i just did a water change 25% and cleaned all the filters as well as scoured the tank for any other dead fish (found a couple dead feeders and removed them), what else can / should i do?