1st grow nutes question

I have 6 feminized skunk strain plants in 3 gallon pots under a 400 watt met hal. lamp. they are a cople of inches high right now , I have only used starter fert. so far. I have some peters pro nutes which is 24-8-16, it says on the bottle to add fert. every 2-4 weeks ... is that enough? and when should I start to use it.I dont want to burn them with to much nutes.. should i start slow and work up?? Thanks guys