I feed mine either meaty foods once a week, or pellets/flakes twice a week. So far it has done nothing but help them grow faster. The rics I've fed are growing about 50% faster than the ones that I do not feed in the short period I've been feeding them (about 2 months now I guess).
I don't think you can harm them by over feeding. Mine stop eating when they've had enough. If anything you're probably just adding nutrients to your system.
Note: If they don't appear to be doing anything when you place food on them... just wait 20 - 30 minutes. Some rics don't have a real visible feeding response (aka closing up around the food), instead they ever so slowly navigate the food towards their mouth and then wrap their mouth around it. It's fascinating to watch -- to me at least.