invincible red/pink stains in primary

Hey guys. I have just finished up my third batch of an IPA. The primary I have been using for these three batches has some small reddish/pinkish spots only on the bottom. I have tried to get these out with a bleach solution, oxy clean, and simple green but they just wont come out. What could this be? My beer has had a strange off flavor all three batches (different recipes from different homebrew stores and have switched to spring water, still there). Any way this could be causing it? I cant imagine how the stains could have gotten there. Any help is appreciated. Thanks!

P.S. - Tried to take pictures but the spots wouldn't show up.

There are possibility of numerous off flavors, perhaps this: How to Brew - By John Palmer - Common Off-Flavors

If you happen to use iodine based sanitizer, it will stain a plastic bucket if left undiluted for a bit.

I've only used star san. I hear that iodine leaves a brownish/orangy color. These are pale pink spots on the bottom. Anyone think I should just make this into a sanitizing bucket and grab a new one?

Red/pink could be a mildew. Mildew is a fungus and it will basically throw down roots into the plastic on your bucket which makes it impossible to get rid of. Given that primary buckets are super cheap, just replace it and save yourself the peace of mind. Don't want to risk another off flavored batch.