Unresolved issue still affecting leaves. Help solve a mystery!

This year I am helping a friend with her grow, and we are seeing problems no one can really diagnose. Periodically the leaves have yellowed in the MIDDLE of the leaves, then it turns white and bleached. Recently, several plants have been browning in the middle pretty bad. Nute burn usually starts at the tips and edges of leaves, plus we have fed virtually nothing to the plants past few weeks except occasional Vermi T, and once a week a quarter dose of Tiger Bloom, same amount of Grow Big as they are transitioning into flower. We figure better to go light on nutes until the plants show a need for them.

These are outdoors in 10 gallon pots of Ocean Forest. They have been flushed several times in the past few months, and we even added some cal mag, the local water is very soft and doesnt have a lot. Took pics to three different hydro shops, and no one can really say what it is. This browning is specific to two plants of the same strain/cutting, one is marginally affected, the other not so much...both have the same care and feeding. The last picture is how the other plants look with the yellowing instead of browning, although they arent too bad, this pic is a real bad area. Any ideas from the info I gave and these pics?

the first ones have that P lock-out look, the the yellow makes me think Mg. interveinal yellowing with necrosis..................

She does PH when feeding to between 6 and 7. Id recommend adding more P but am afraid adding stuff may make things worse. And why would one plant be so affected and others not?

I agree the first leaves def look like they have a phosphorous deficiency though I would lean more towards the beginnings of iron deficiency than mg

Iron.......man

If it IS lockout, a PH question. We use the water ph tester and adjust any feeding to yellow to lime green....so 6 to 7 ph. But if the testing vial isn't emptied, next day it is blue. Does that mean we SHOULDN'T ph when feeding, or does the ph on what we feed matter at the time it is applied?

Has it been hot and plants in full sun without a 'rest' in shade middle of day?.(eg shading tree to reduce stress for an hour or 2), maybe the shade leaves are suffering heat/light burn. I have no doubt the last pic is light/heat burn.

Even in the sun the preferred temp is 80 and above this the plant will stress, stunt and burn, at 100+ its lockdown mainly indicas. A perfect day for a dope plant is cloudy, bright glarey(summer) and about 80 deg.

Ive been in this area for years, and normal summer temps are in the nineties to low one hundreds. Never seen anything like this before. And the affected leaves are not at the very top, at
least as far as the yellowing picture, it's the mid level leaves. Quite honestly, when the temps are around one hundred, the plants go though a growth spurt. If they have enough water, they love the sun and heat

I recommend foliar feeding 1/4-1/2 strength veg nutes to see if it makes a difference,it only takes a light cycle to notice.If the greens starts to come back then give it a full dose of veg nutes.
If lockout is the case then your friend needs to get use to misting (And flushing to get the salt buildup out the soil).Hope this helps

obijohn said:

She does PH when feeding to between 6 and 7. Id recommend adding more P but am afraid adding stuff may make things worse. And why would one plant be so affected and others not?

Click to expand...

Check this for a side by side view of one plant affected and one not.
http://en.wikipedia.org/wiki/Chlorosis

Plant may not be the same type but that is irrelevant.

When confronted with uncertain def the safe bet is usually 1/2 strength feeding of a balanced organic plant food like 20-20-20 as long as it it organic it can only help it will not burn. It aids in undoing a nute lock out.