It actually depends on the size of the cricket, and the size of the trap. Generally you don't want to feed your VFT anything bigger than 1/3 the trap's size.
Baby crickets are usually fine - I bought a bunch at Petsmart and let them have babies, let the big ones go, and then the VFT's ate the babies. Pretty greusome, huh?
The only thing with this is, crickets CAN get a certain fungus if they are kept in a humid environment with poor ventilation, so if you have your VFT's in a tank, and it is not ventilated well enough, avoid the crickets.
Also, are you sure it is mold, or is the trap just turning black? Turning black after eating is normal for a trap.
Hope that helps.