Finding and using the right plant food

I have plants in various stages og growth one 2 1/2 month and 2 1 month and five one day olds.I went to the store looking for just pottasium and nitrogen but could't it find it by itself. and I bought "Expert Gardener" warer soluable plant food with N-P-K- amonts of 10-52-10.Is this okay for my plants?In what amounts should I Use? Lowes and Wal-Mart garden centers didn't carry polymer crystal for reduced watering,doe's anyone know where to get these?

You want follow the directions on the bottle,but use 1/4 - 1/2 of what they are recommending.And i wouldnt use anything on the babies til they are a few weeks old. Good Luck