I think it's a K and Mg deficiency? Can someone else verify for me please??

1st week of flower. Hydroponic water farm in hydroton. Temps about 70-80F. Res temps about 18C. RH about 25-40%. pH is 5.9-6.2. Using Advanced Nutrients 3-part base with B-52 B vit supplement, and Voodoo Juice beneficial bacteria. Yellowing between the veins on the top leaves. Dark spots occurring on the middle-top leaves. Not very much though. Everything else looks green and great. Roots are white and taking up atleast half of the res. Any ideas? I'm thinking K and/or Mg deficiency? What do you think? Does she look hungry at all?

Yeah i think its a Calcium magnesium thing... my SLH started getting 'bent' leaves so i added CAL MAG to help.. looks like its working; i hate coco coir.
either that or its a PH lockout of somekind. what medium are you using?

i dont do hydroponics...nothing aginst it just have always done soil....but id say that looks like magnusium deffenciey...wouldnt you want to have it a little lower around 5.5....just asking....but theres a guide to nutrient deffenciey/toxicity in the grow room under marijuana problems

Yeah, I mean, 5.5 is the lowest. Idealy you want it about 5.8. The plant releases enzymes and hormones into the reservoir to assist in nutrient uptake causing pH to fluctuate sometimes. It's nothing major. Like +/- .2 or .3 of a pH point. Amount of nutrients consumed along with water intake also have a roll to play in it. More nutrients uptake = increased pH. More water uptake than nutes = lower pH. Lock out really only occurs at 5.0 or lower/7.0 or higher.

I foliar fed with 2.5 mg/1 quart just now. Let's see if that solves this here problem. I'm hoping for atleast a qtr pound from her in 7 weeks.

You will have to raise the light as your bleaching the chlorophyll out of the upper most leaves.

What gives with the spots on the leaves then? Is that something else?

Question Mark?

spots between the veins usually means mag issues... lock out or not enough... i always say "lock out" vs not enough... if possible when you have stressed plants, start fresh with clean ph water let it run a few days to help the plant flush its salt content out... i do this every other water change...

I agree with buds... Your lights are to close.. That there is light stress as u can see the chlorosis is at the top of the plant.

Got it! Thanks guys. Looks like it fixed itself after I raised the lights.