light areas on skin while basking??

I am back with new troubles, which I hope mean nothing. My dear Darwin (he will be 7 years old Feb 10th!) and I are struggling thru another long NH winter. Try as I might to fatten him up beforehand this year was even more difficult and met with little success - sometimes I think the only reason he is still here is due to our mutual love for each other :love5:

I have noticed in the last 2 days that when he basks there is a light area on one side - (where the liver is?). There is also an area on the side of his head - first noticed this one about a week ago. They both remain for quite a long time after he leaves the heat. :-/

Are these anything to worry about?? Have others experienced this? See pics below.

A Note:
A couple of folks will remember us from the past (I don't post much) but many won't so I ask in advance that no one comment on hydration or other things that you might think are wrong with him. He has a long history (you can do a search, if you'd like) and I suspect (as does one of my vets) the adenovirus. He's been with me since he was just 2 1/2 months out of his shell and has always gotten the very best care. I hope this does not sound harsh, I just want to focus on the issue at hand. Please do ask any questions that you think might be helpful. Thanks for understanding!

lele & Darwin

I hope I didn't deter people from comments with my "note" about his history/health. I'd have hoped that someone would have responded by now :-/