nitrogen deficiency 2 weeks into flowering

[smokingdog]

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.

 

[Treetroit City]

N def usually starts at the bottom of the plant and works it way up.

May be too close to the light for its liking?

 

[Floridian]

Just because you change photoperiods doesnt necessarily mean you should change ferts,for the first couple three weeks of 12/12 is when nitrogen is needed most during the stretch.You should also feed phosphorouus when you change cycles,just not nearly as much as nitrogen