Baby mushrooms can have a white color. I have tons of greens. Not even going to try to count them. When new ones grow out of the rock they are translucent and with no green at all.
But then maybe you do have white ones. Never heard of white ones myself.
So you think they have a chance. Old owner had them under normal t5's and was running his water at 68 F....:frustrat: I have them in 78f with some t5 HO's
Wow! What did they look like when the old owner had them? They probably just need to light acclimate to your stronger lighting so it will be a wait and see thing.