Tongue Is Red Help!

I picked up my leopard gecko from ++++++++ back in July. He is kept on eco earth with some caves made out of excavator clay. No lights just a heat mat under his warm hide. I was feeding him yesterday and I noticed his tongue was awfully red. I read somewhere it might be calcium deficiency but I don't understand how that would be possible when all of his food gets dusted. I'm really worried does anyone know what's wrong.

I've seen that in some of my geckos as well. It's fine. I don't think there's any way to diagnose a calcium deficiency (that I've ever heard of) by looking at the tongue.

Aliza