That is a lot of food for two clowns. I would do maybe 1/4 cube everyday, or 1/2 a cube every other day. If they are already plump (which I'm assuming they are) just monitor how they do. I feed my 125g 1 cube of frozen brine or the equivalent of PE mysis once every other day and all my fish are plump and happy as can be.
If they're hungry, they'll eat the food on the ground. No need to feed them again. If you're worried, you can try to target feed with a long syringe. The stuff on the ground is just decomposing and adding to your cyano