outdoor plant control (lemon skunk & thai ss)

im a beginner so i accidentally chose late flowering strains which arent good for my region. they still havent started flowering so i switched from my high in nitrogen miracle grow (which despite alot of criticism it has worked very well). i used it beacause all of my bottom leaves where dying do to lack of nitrogen. after i used the mg they bushed out quite nice. i tryed to speed up the flowering process with miracle bloom booster but i believe i may have over done it b/c a few leaf tips turned blackish. i am also having a small problem with pests. its not a terrible problem but it is still a decent problem. would seven dust or any other low price products that i could buy at lowes be much help for the pests and still be safe for my plants. my main concern is that since i am having these issues while they are in the vegative stage will this affect the yield much ???? please enlighten this noobe !