Help? Heat/Light Stress or Deficiency?

Responses appreciated!

I am in my 3rd week of flower, and have noticed some sudden necrosis in the leaf margins at the top of the plant. There seem to be no other issues with the rest of the plant, and no deficiency I know of seems to be a match photogenically. PH is buffered by dolomite lime to 6.5, and she just got a mild dose of Tiger Bloom and Cali Magic. Temps in the tent are 77-79 degrees and the humidity sits around 45-50.

I recently retired the old 600W (true watt) LED that the plants have been under for over a month that was at 20" away (31,000 lux at center), for the Duo Lux 600 that was sitting at 36" for 2 days (51,000 lux). Yesterday I moved the light down to 30' (56,000 lux), and that's been the only thing done in the tent through today when I found the burning on the leaves.

Burns are only on a few leaves, all under the middle area of the light and on the top leaves only.

Pretty sure It's light/heat stress, but it looks nothing like what I've seen happens with heat stress.

Other plant is unaffected (left side of group picture).

Looks like early phosphorus deficiency, that's just my opinion though, plants look good though

Thanks for your input! Was another option that came to mind, but she should be good on phosphorus as far as I can tell. No real reason to have a lockout, PH has been stable and I always go easy on feedings. Could also be that I just didn't notice these marks till now and she was thirsty for phosphorus after the last plain water feeding- they are very hard to see unless you're close up.

Bibity bobity bump!

New pics, tallest growth appears very lime green-yellow. The areas effected by this have decreased bud growth, some orange hairs already, and the burn marks in the margins has not spread (has just darkened).

Soil PH was 6.8, (usually goes up as she needs to be watered). Going to water tomorrow.

Note: picture near the right edge of my tent screen frame is unaffected and has normal bud development.

Real evidence.

Lower to middle of plant, only 1 leaf.

Starting to lean toward phosphorus now. Redish purple petioles and striped stalk join the canopy. Part I don't get is its only present in the area of most light concentration when it comes to the canopy. Her PH is 6.7. I gave her light foliar Epsom, and watered just enough to wet her through soil to eliminate sulfur and magnesium.

This community is not what it once was. Good talk guys. Moving to a new site.

Its still possible to lockout/slow phosphorus uptake by using too much calcium,not easy but ive seen people do it multiple times. Since you say it's got P then its worth the note.

-tiger bloom has calcium
-calimagic has calcium & alot of it
-dolomite lime has calcium and can be problematic if too much is added
Hell if your using tap water then its a very good chance that's got calcium in it too....

^^^^ I figured exactly that out a day or two later, it is a result of using powdered dolomite lime as a buffer. Too much calcium became available over time for the plant which is what caused bits and pieces of Magnesium, potassium, iron, and manganese deficiency symptoms (the new intensity of my light accelerated this).
To fix it I cut down the 5 gal smart pots and gently scraped the lime deposits off the sides of the dirt balls (it was quite crusty). I then very carefully sleeved them back up with 7 gallon smart pots and filled the empty 2+ gallons of space with ffof&perilite (no lime). I slowly watered them through with plain distilled water. 2 days later I flushed them with 2 gal of sledgehammer amended water, let it soak for 45 mins and followed up with 3 gallons of plain 7.0. Finished the flush with a weak 500 ppm wide range of nutrients (no calcium!) and some beneficial microbes for the roots. All of the symptoms have seemingly halted, and bud growth is resuming it's normal pace just in time for week 5 of flowering (10-12 week strain).

Don't use powdered dolomite lime to buffer! If you do, do so sparingly!

Plant on left is the one that was choking on calcium. Lady on the right is a beast that don't give a F%!K, just needed more room for her roots to breathe. (Soil was very compact).

Diamondbuds said:

^^^^ I figured exactly that out a day or two later, it is a result of using powdered dolomite lime as a buffer. Too much calcium became available over time for the plant which is what caused bits and pieces of Magnesium, potassium, iron, and manganese deficiency symptoms (the new intensity of my light accelerated this).
To fix it I cut down the 5 gal smart pots and gently scraped the lime deposits off the sides of the dirt balls (it was quite crusty). I then very carefully sleeved them back up with 7 gallon smart pots and filled the empty 2+ gallons of space with ffof&perilite (no lime). I slowly watered them through with plain distilled water. 2 days later I flushed them with 2 gal of sledgehammer amended water, let it soak for 45 mins and followed up with 3 gallons of plain 7.0. Finished the flush with a weak 500 ppm wide range of nutrients (no calcium!) and some beneficial microbes for the roots. All of the symptoms have seemingly halted, and bud growth is resuming it's normal pace just in time for week 5 of flowering (10-12 week strain).

Don't use powdered dolomite lime to buffer! If you do, do so sparingly!

Plant on left is the one that was choking on calcium. Lady on the right is a beast that don't give a F%!K, just needed more room for her roots to breathe. (Soil was very compact).

Click to expand...

Yes, too much calcium in veg can show hints of mag lock & too much calcium in flower will show hints of mag/phos lock and some strains/phenos can be more sensitive to this then others.

First of all, thank you generously for the replies- I thought nobody knew wtf to think of my post.

Been a few weeks, but got it sorted out. Had to flush that same way twice more with a single feeding between flushes, and all of the symptoms stopped. Bud growth resumed, and is now lookin pretty awesome. According to trichs, I'm 7-14 days from choppin day. Just started the harvest flush and I've got some bud porn for anyone who cares to check them out. With the powerful aroma of one hundred skunky grapefruits, I present to you one of the new strains from Nirvanashop, Lemon OG Haze: