Used tank with colored spots in silicone...
Picked up a used 29 gallon today. It looked like it just needed a good cleaning on first inspection but upon getting it home I see there are some colored "mold-ish" looking spots along the seals, many of which appear to be somewhat brightly colored and a few are almost purple. They seem to be under the silicone although the seal itself does appear to be largely intact. Any ideas on what this could be?
Update: Figured it out with some help from the chatroom. Thanks guys!