This is quite coincidence, just yesterday one of my friend who use BP asked me about cloudines what hapened to him due to BP usage. I tell him that I was not aware of that situation and I never readed about that issue. And now we have few same issue from diferent part of the world. My friend use slow flow throu fluid. reactors, no carbon dosing, new aquarium, low bio load... nothing what IMO can trigger bacterial bloom. He dont have any loses and fishes are not afected at all, soft corals was closed and only livestock afected from those bacterial bloom. He actualy try few times to disconect the bp and every time when he try again with bio pellets aquarium get cloudy, without BP aquarium are crystal clear. He use very strong skimmer reef octopus super skimmer 5000 on 500 liters aquarium and only 500 ml of BP. Only what can come to my mind as a trigger what created those issue is that he used sponge inside the reactor who get cloged from bacterial bio mass and slow the fluidisation considerably(creating first bacterial bloom), he remove the sponge but he do not washed BP and probably inside the reactor was created high bacterial bio mass what cloud the aquarium after he start the BP again.
I use BP in same fluid reactor, also use them in 3 aquariums with diferent reactors and never get the bacterial bloom even I had issue with protection sponge inside the reactor what almost stoped completly flow through the reactor and create bacterial bloom inside the reactor what I intentionaly pour in aquarium to see the efect and feed the invertbrates who like bacteria, I dont had any problems with my livestock when I release the bacteria from reactor in aquarium but I inject air together with bacteria to compensate oxygen loss and low pH.