I believe we are at a point where we may need to consider the vet. He is showing no signs of pain or discomfort, but then cats often do not. I noticed last night that he didn't seem as keen on his food as soon as I had it down; He ate it over the course of the evening, but it's not like him to not pounce on it. we spend so much time with the cats that we see any little change from the norm. It's all a bit sad really, although I think we might need to consider a check up to see what's going on.