I store my fermentors filled with water and bleach. I was getting ready to use one today, and when rinsing, I noticed a few dark dots inside the bucket. I tried to wipe them off with a paper towel and then I tried to run my fingernail over the spot and it seems like the spots are imbedded in the plastic. Since it seems to be embedded in the plastic, I think I am okay, but I don't want to risk contamination with mold. Do you think these spots are a problem?