Buckets can get microscopic abrasions on them that act as hiding places for yeast and bacteria during your sanitation process. This might be a sign for you to replace your buckets. As well it is good practice when using plastic to avoid using any abrasive scrubbers (ie the green scrubby) when cleaning, stick to a soft sponge when cleaning plastic. In addition you should consider adding a hot caustic wash (PBW or Oxyclean) followed by a hot Acid rinse (Star-san) before putting your plastic fermenters away.
As for this batch, let it ferment out. See how it is. Toss the bucket it is in, and if you bottle it, be careful, read about bottling with brettanomyces, and use tubes and bottling buckets that you will not use for your other beers.
Another good test to, is to take a bit of wort, next time you brew and put it in to a sanitized glass jar, or pyrex flask, cover the opening with foil, and let it sit out.
If it takes less than a week to start fermenting, you have a sanitation problem post boil, during you cooling process. If it takes a week or longer the problem was with your fermenter.