Hi, I have a RES about to have his 2nd birthday. He seems happy and healthy and all is Ok with him, but I have just started noticing a small spot on his shell, just above the half-way mark if looking from his head to tail. It's not noticable most of the time but when the light hits it right, you can see a small shiny spot, a semi-circle about 1/4" in diameter. It almost looks like he has a small piece of aluminum foil stuck to him. Has anyone else experienced something like this and do you know what it is and what causes it? Thank you!