I got a Russian Tortoise 6 months ago, he has had these indentions on his shell i thought theyd go away with time, does this look like a minor dry shell rot or is it not much to worry about?? I have him on coco coir bedding, shallow water bowl in the terrarium, and tube uvb and heat lamp, the warm side like 85 and cool side 65-75. The coco coir is damp but not at the surface