Phosphorus? What's causing this leaf issue?

Hi, I'm having an issue that I initially thought was heat stress, but seems to have progressed. Can someone please confirm that this is a phosphorus deficiency? I flushed a bit today and yesterday and I added a bit of water with a few drops of lemon juice in them to lower the pH. I found out tap water in my area has a pH of about 9, and I have only used tap water once - to wet the soil before I transplanted... Oops?

Anyway, here is a picture that shows the leaves with issues.

Thanks in advance!

Yeah Man, possibly a phophorous deficiency. However it could also b that ur medium is too rich. But u will know if u have been over feeding them or not.

I would say its a Phophorous deficiency thou. If ur PH is around a 9 like u say then thats obviously a problem. Anything much higher than a 6.5-7.0 maximum and u risk getn nutrient lockouts as ur roots dont work properly, and this sounds like wat has happened.

Hope this helps and sorry that it took some1 over 2 1/2hrs to answer this.

I'll confirm, clear P deficiency... the darkened sections between the leaf veins is a clear sign. I also see K deficiencies. I'm not for sure if it is an overly high pH as P/K are usually available up high... the micros can't be absorbed in this area. Without more info it is tough to say. The solution could be out of balance & a change is the solution (no pun intended). The pH could be very low & an adjustment is the answer. The nute levels may simply be low & an increase in dosage is the answer. Perhaps levels are okay & initial pH is okay, but it is swinging & there is no control... higher levels of monitoring may be the answer. It depends, but P/K for sure. Best.

Cool, thanks for the help. I flushed the last two nights with a slightly acidic solution of lemon juice and brita filtered water (I microwaved that water for about a minute to make it lukewarm). I also added 2 ml of thrive alive to my second flush (I'm planning to take clones soon). I rinsed the leaves 3 nights ago and did a mild foliar feed last night (2 ml in 1 L of water in a spray bottle). I think lowering the pH helped a lot, I'm noticing growth seemed to have picked back up again. I haven't used any other nutes, I'm 18 days in from clone, and I've had her planted in FFOF for about 16 of those. My cab is coming, so I should get whatever nutes come with it, and I can decide whether to go with those or pick up some other ones from the grow shop. I've been holding off on dropping the money on more nutes until I knew what I had coming.

Hopefully the flushes will take care of the lockout. I should have the meters and nutes in hand in 12 hours, so I think we'll be fine . Here's an update pic or 3, did a bit more LST.

PH ph ph ph ph ph

I flushed a couple gallons of water that I boiled and then cooled, and added a teaspoon of 3% H2O2 to oxygenate the roots plus about 1 ml of thrive alive. I flushed one pitcher at a time and went through the whole cool, test, add, test, flush process one pitcher at a time. My cab should be here any minute now, and I'll get a better pH reading.