Hi Angie,
I am not experienced with growing many cacti or succulents but I'm always wary of using any fertilizer or plant food full strength. Many years ago some of my plants experienced fertilizer burn so I began to use much less than the recommended amount listed on the container. If it states to use 1 Tbsp. to a gallon of water I always use 1/2 Tbsp. but that's just me ... and I must admit that I'm really bad about feeding my plants on a regular basis.
Hopefully those who grow succulents will pop in with suggestions on whether you should be fertilizing you young succulents.