I've been noticing that when I get the girls fresh water, there have been some black mold spots inside the waterer that easily come off with my fingernail. I add ACV w/ the mother to their water every time. Can this be the culprit? I've also heard that Clorox can be added to their drinking water to eliminate mold build up in the waterer. Is this true and if so, how much would I need to add per gallon? Is it okay for the chickens to ingest a small amount of Clorox? Thanks in advance!!