You should be feeding your corns more often. Invest in a scale that weighs in grams. Give them 10 to 15% of their body weight. I just upgraded my corns to medium sized adult mice. I freaked out cause I thought that size was too large, but they take them just fine. My corns are about 150g atm. I feed them every 7 days and they still act like they're starved to death, so feeding response in corns is not an indication of how often they should be fed.
(oops, got Phoenix around around my wrist as we speak and she crawled up on the keyboard under my hand and got "typed" on. ow)
Edit: I should say the 10 to 15% guideline is as they are growing, adults are fed a bit less. Since you said you were feeding fuzzies, I assumed yours is small. (oops, Phoenix just fell to the floor, time to put her back)