I am in week 4 of flowering for my first grow. i made the mistake of getting 5 diff strains in one box but of well. Im using a 400w hps 12/12. Ive been using fox farm nutrients until about a week and a half ago when the tips started to burn. I think its nutrient burn but im not sure any idea? For the past week and a half i have just gave it water no nutrients, when is it safe to give them there food back? thanx.