gh trio

So I need to add Nitrogen to my DWC bucket. I'm using GH Trio. My problem is that the Floramicro is the only one that contains a good amount of N but everything I read says it must be added BEFORE the other nutes. Can I add more to an already mixed solution or will this cause problems?

Same Cab,Same Strain but this time the Nute feed has been and will continue to be stronger than last grow using GH Trio and soft tap water. I am awaiting my Mars II 400 for flower, which by time it arrives my plant will be just starting to bud. Right now it's a 2 gallon growbag filled with...