TizMyLife

I had 7 plecos about 2 inches long. 4 in one tank and 3 in an adjacent tank both with guppies. I have been feeding them algae wafers and cholla wood. This morning I went to feed and 6 of them were dead, floating on he surface with their stomachs looking like they were eaten away. Wha could have happened? The guppies are all fine and the remaining pleco appears fine! What do I do?