I have tried to take your picture and enhance it, however not any better of a visual. Can you take a better, closer and clearer picture, honestly i can not distinguish anything clearly form your original posted picture!
I think the tortoise needs to be seen by a tortoise vet.
Can you give us a bit of info as to what you feed the tortoise and what his living arrangements are like?
If memory serves, you have radiated, sulcata and aldabran and you allow them to be together. It just might be that mixing species has caused your illness problem with the Aldabran tortoise.