I wait for 2 sets of full leaves,hit it with 1/4 dose ,I'm not a pro but rarely bat less than z per foot ratio. It depends completely on nutrition concentration. And every seed pheno wants more or less of it. I ease into it unless it's a clone that's been through before. If it's a new strain I go up 10% each time until I see slight burn then back off 1 step. Keep it healthy green and the rewards are denser,danker,and stinkier