YELLOWING LEAVES!!

[wardrobe grower 78]

here is a pic of a set of leaves yellowing on a few plants of mine,think it may be due to a lack of N although i dont know as im using my fert(bio-grow)as instructed on the bottle
any1 with experience of this fert could maybe give me a few pointers as to what may be goin wrong?

[marijuanamat]

are you vegging or flowering at the mo?and what is the N-P-K of your fert?

[Proof]

Looks like zink Deficiencie to me

[wardrobe grower 78]

theres just over 4 weeks into veg from seed,im usin bio-grow liquid fertilizer which says 8% nitrogen-2% phophorus and 6% potassium which on a grow chart i got with the product says mix 1ml fert with 1 litre of water and to use it weekly which i have been doin and just usin plain water inbetween weekly fert.there under a 250watt MH about 13-14" above the canopy with fart fan extractor

[dHazed]

come on guys that is clearly a magnesium deff add 2 tsp of epsom salts per gallon of fert to correct