Another thought is can pathogens get in through the air pump and air stone, that's what I think is a good possibility, yes the aquarium filter has a crude filter but I don't think that stop's everything... I'm thinking the air pump is the culprit as nothing else seems to be wrong, however I did have 4 times to strong nute mix so yeh lol that to, but I'm installing a 32w UV sterilizer so that should stop any further blooms. What is the recommended to run this UV as I heard about 1 hour a day ?