I just received a fully serviced canon ql17 that seemed to check out great but on closer inspection I noticed a yellow ring around the edge of the rear lens element. It is crusty looking in nature which leads me to believe it is the cement coming undone from the element is this right? I'm curious if this is common or not in the canonets and is nothing to be concerned about or will it eventually get worse and I would need to have it replaced in the near future.