no ideas on what is going on if everything else is fine meaning ammonia and nitrite level and all or is it just a bio bloom and the heat was maybe to high???
By the looks of you pics and the behavior of your fish I would say your tank has both high ammonia and nitrites. I would recommend that you get a new test kit to confirm you original readings
wow their fine my girl did the 25% water change omg she said they are all back to normal omg I almost lost it there thanks people so much love you guys that was a trip in a half