HELP! Leaves yellowing between veins HELP PLEASE!

[Jaycee77413]

Hey there i have grown 1 4x4 tent b4 this with a general hydroponics nutrient regiment in coco under a 2000w burple light .... didnt yield a ton for thier being 4 plants so doing some reading i purchased a spiderfarmer sf4000 quantum board and ever sence i have been getting yellowing in between the veins of top leaves .... i turnned this light down as much as i can and it is 40+in away from my plants same nutes and watering schedule along wit a 5.8 ph level which is perfect for coco coir .... please give me some advice of what im not doing correctly here ...... the 3rd pic is one of my 4 outdoor plants using the same nutes and water! Thanks for the help?

 

[bboyfromwayback]

It looks like it needs some CalMag to me. Give it a good dose with the ph up a little so the plant can use it.

 

[BakedMoose]

From the first picture, I'd say it looks magnesium hungry, and I'd generally use epsom salts for it (magnesium sulfate).