I've read the threads about using ACV with the Mother in waterers. So I scrubbed and rinsed with a bleach solution, rinsed our 5 gallon plastic waterer and added 1 Tbs ACV for each gallon of water (I only fill it with 3 gallons so I can still carry it). No problem until I went to change the water 4 days later and there were slimmy black spots on the sides of the waterer. I repeated the cleaning process and soaked the entire waterer in a bleach solution....and the spots appeared again after 4 days. Is this normal when using ACV?