Are mushrooms with interior holes ok? When I started to cut up these store bought mushrooms, I saw there were holes in them. There weren't any holes or spots visible on the exterior. Are they still safe to eat? They also started to turn a bit pink after cutting, maybe some oxidation but it seems unusual. 

I buy these all the time and I've never seen these kind of holes in them.
Those holes are most likely caused by some kind of larva(pdf), such as mushroom maggots.

While disgusting, such larva are harmless to humans, and the holes they leave behind are equally harmless. Since you just seem to have the holes, I wouldn't worry about it.