Why are my hermit crabs suddenly so active?

I'm new to the world of caring for hermit crabs, but I like to know everything I possibly can about new things, so I've been doing A LOT of research online about them. I've had them for about 5 months, and they've all been doing quite well (I have 5 of them... 3 are Purple Pinchers and 2 are Equadorian). Recently I read that the pellet food you get at the pet store was bad because of the preservatives in them, so I threw it out and started giving them fresh fruits, veggies, and egg shells. About 2 days after I started feeding them fresh foods, they became super active, mostly during the day time! I know they're nocturnal animals, but my crabs for some reason are crawling and climbing everywhere 24/7. It's like they're on speed or something. Could this be because I started giving them fresh food? Can it make that big of a difference? I know humans obviously function better on preservative free food, but has anyone ever heard of their crabs gaining crazy energy just from switching their food?