nitrogen deficiency 2 weeks into flowering

my m8 has 5 bf blue cheese on there 2nd week of flowering it only seems to be affecting the 1 plant a few of the top leaves are starting to get a bit brighter than the rest an im sure it's a nitrogen problem,he's using DUTCH PRO A & B BLOOM an DUTCH PRO EXPLODE with a drop of HESI super vit.
They a fussy feeders the blue cheese so there not on a great deal of nutes at the moment there only getting 3.8ml of A & B an 2ML of EXPLODE per 6ltrs of water the other 4 are all doing great there looking very healthy it just seems to be this 1 plant it's the 1 that is directly under the hps'if it was given epsom salts while in flower or a bit of the A & B veg feed would that sort it out or make a small problem a big problem.

Pix? It could be too close to the light, maybe, as it is directly under it, I'd be surprised if it was an N def in the flowering stage, could very well be but without a pic it's hard to know, epsom should be alright as long as it's a LOW dose, as I like to flush with ice-water/my own fermented sweetener blend/epsom salts and it's never given me an issue at ya 6-12 weeks in; so at week 2 it should be safe, but the E.Salts I get don't have N, so if that's what you're assuming it is, find ES with traces of N, I wouldn't use them if the levels are above .5-1%. Try something like Primordial Earth's Super Green or another supplemental, FloraBlend is cheap (like $10-12 a litre) and is a booster, NPK at .5-1-1% plus it's got other trace and micro nutes, and it's Veganic (if that matters to ya). It doesn't do a lot for plants but it's a good stabilizer, as it's weak enough not to really run the risk of burning yer gals but is strong enough to help with deficiencies and it's great in the beginning of flowering and the end (last 1-3wks, depending on flower time). The grow I'm doing now is all experimentation and am gonna try using a splash of this in the flush on a couple of'em. Hope this helps! If not post a pic!

I should note that the epsom etc. flush is the FIRST flush, it follows the FloraKleen, after it's finished dripping (about an hour or two) I flush with that mix. The second and final flush is done 5-10 days later with nothing but maybe ice; wait 24 hrs then give total darkness for 24-48hr and then it's time for my Fiskars to get sharpened!