white dots on head

Hi, I have a 12 inch Rivulatus in a 90 gallon tank with 2 plecos. The tank is being filtered by 2 Aquaclear 110s. I'm using a 250 watt aqueon pro heater set to about 78° Fahrenheit. Lots of big water changes and I'm currantly feeding (or at least trying to feed) Fluval bug bites pleco and...