So I have 6 plants in a my rez and the biggest one is showing some yellow on the tips. All the other girls look fine so I am leaning toward a defiency rather than too much nutes. Am I right and what should I do for the next step. I am using 1/2 of what GH nute calculator reccomends since it is warm up in this bitch. plz help if you have time, thanks a grip ton...