if u have a hydro shop in town tell them ur prob.. obviously not say its weed, say its tomatoes... if not, got to wall mart or sumthin and get what u thinks best.... they will say veg, bloom on it... the nute value will be on it looking like 10-14-10 or whatever.. thats the n-p-k ratio... veg high in (n), bloom high in (p)... also look on the side and see if there is secondary nutes such as iron, magnesium, ect.. jus dont go crazy... give it 1/4-1/2 the recomended dose and wait a few days atleast b4 feeding more... those "comercial" nutes they sell in stores r stong and not intended for MJ but wll work fine if u use it rite... like i said too high of dose or too often tryin to fix it, will lead to new probs and u may think that its "this" when its really "that".. if ur water is yellow, maybe its gettin too much thats in ur soil, thats y i dont like MG soil.. hard to determine what the prob is but if u havent any probs till now, ide say lack of nutes... gl!!