Mysterious Yellowing Between Leaf Veins

Hey, heres my setup

Soiless - Peatmoss/perlite/ewc
Flowering Week 5
Fox Farm nutrient line - Water ph'd to 5.3-6.0
1/2 nutrient strength
600 watt HPS - about 1.5 feet from the glass to bud
Room temp - 79-82 hum - 40-50%
-They have been slowly yellowing more and more over the past few weeks.
-The leaf tips are not brown or crispy but the leaves feel a little dry
-The other plant of the same strain is dark green, but also about 80% as big.

I have been reading up on this and I think I narrowed it down to 2 things.

Yellowing Between Leaf Veins
This is likely a potassium deficiency. Add to your water or correct a PH balance. Potassium can also be locked out by salt buildup so if your PH is correct you may try a flush before adjusting nutrients.

Click to expand...

Leaves Turn Pale Yellow or White with Green Veins
This is a sign of iron deficiency. Add more trace nutrients or chelated iron. As always, PH imbalance could also be the culprit.

Click to expand...

They both seem like they could be a possibility. Can anyone help?

check the ph in the soil and you should also check to see if you have a bug problem

Looks like classic magnesium deficiency. (yellowing with green veins)

You could gets some cal/mag or give it a shot of a complete hydro fert. But it won't make the plant get better, just stops it from getting worse.

Unfortunately you are getting close to harvest time and the window to fix deficiencies is closing fast.

hope that helps some


Porky

As the plant is getting bigger its slowly becoming def to everything. Why are you still using 1/2 str, the maker of this product has a recomended dose for maximum effect so it doesnt get deficient like this.

sorry about my last post i dident take a good look porky b is right this is your problem and trust me ive been doing this for ten years i know my stuff......

your problem is MAGNESIUM DEFICIENCY:
Problem: The edges of the leaves may become yellow or bright green and may start feeling crispy to the touch. The light green or yellow coloring may also effect the veins of the leaves.
Solution: It is very important to maintain a proper pH in order to avoid a magnesium deficiency. Adding more magnesium to a system when there is a pH lock-out will only make the situation worse because the plant will not be able to absorb any magnesium until the pH has been corrected. Flush the system with properly pH'ed water that contains a full set of proper nutrients and see if the new growth starts looking healthier.
HERE IS A PIC OF A PLANT WIT MAGNESIUM DEFICIEENCY

Nice, thanks for the responses.

I didn't start ph'ing my water until week 3 - but it has been at 6.3-6.4 with out me adding any ph down/up and using regular nut schedule.

Awesome, I bought cal-mag just the other day so ill give them a good flush with that and see how it goes.

thanks again!

edit: oh ya and i use 1/2 strength because tap water is being used

for sure a cal/mag issue...unsulphured molasses works just as good as cal/mag, and cheaper...also has iron in it.