I have a 13 year old (approx.) leopard gecko. She has been the easiest pet I've ever owned. but recently (about two months ago) went online to check what forums were saying about substrates, and everyone was SUPER against sand. And i get it, if they eat it theyll get impaction and die. Ive had Larry on sand her whole life and never noticed any problems, but i thought id change it. So i went to the pet store, got her a new substrate (they recommended wood chips). I changed over about two months ago. Since then, Larry's colour has been getting darker and darker, and shes been shedding very poorly. the skin she sheds is very thin and sometimes doesnt come off, leaving patches of dry, tight skin. I got very worried so I've changed her back to sand today. 13 years of happy living on sand, maybe she was getting something from the sand that i didnt know about. Any thoughts?