sunburn or other on mammillaria albi

[aliazurius]

Hello this plant is a mature mammillaria. First is it albilanata?. Ever since i got it, it has been so light sensitive. Even my grow light seems to sunburn it.
The roots look dry when inspecting but otherwise healthy...no lumps. I've been caring for it for 2 years now and the sunburn has spread. It has stayed very warm, 50 deg f minimum.

Please tell me what you think it could be...I hope not spider mites. Nothing is soft but i know its probably more than corking...

[greenknight]

Not 100% sure, but I would say Mammillaria chionocephala.

I can't see anything wrong with it - what is this problem you're referring to?

[Arcturus]

Many cacti have that kind of color at the base, both in the wild and in the pot. Mine have it as well. But their tops are green and healthy looking. They've been like this for many years. I guess it's normal.