Is This Potassium Deficiency?

[unkied]

Hoping somebody can help nail down what's wrong with my plants. 4 feminized White Widows, 46 days old, 7 days since switch over to 12/12. 1 day after switch, 1 plant started getting brown edges/tips on one branch. The leaves were about in the middle of the plant. A day or 2 later a 2nd plant started having the same issue, again very localized. As I examined the plants, I then cut off the bad leaves. 24 hours later, the symptom reappear so I know its not going away. Then yesterday a 3rd plant also started showing same symptoms.

Here's a shot of 1 of the plants:

and here is a shot of another plant:

I am new to this stuff, and have been googling like mad the last week or so, trying to figure this out myself.
This to me looks like the descriptions of Potassium Deficiency but I don't see that 'yellowing' that most sites describe as showing up just inside the brown edges. The plants are in 5 gallon fabric pots, with FFOF soil. I have been feeding them a solution of Jacks 20-20-20 combined with a little Maxicrop Soluble Seaweed (0-0-17), limited to a PPM of about 600-800. The PH is between 6.2 and 6.4. Since I know I have fed them nuts with high K, I figured maybe it was ? lockout ? so I gave the affected plants a flush. No luck after a few days - the problem is still showing up.

Any insight would be GREATLY appreciated. Thanks.

 

[KingJoe83]

lets take a look together ?

Flush brown tips mean to me sulphur build up maybe ? Or

 

[unkied]

Hi King, just back from work. Thanks for replying! I had some trouble trying to track down any info on Sulphur Excess but did manage to find it shown in one of Jorge Cervantes' charts:

It does seem to show something Similar to what I see with my plants, but A) it shows that same problem for BOTH deficiency and excess?! and B) its just a drawing. I'm really not sure how this could be the cause tho, since I treat all the plants equally, and have been, for the most part, not given any excessive dose of nutrients that I recall. However since this problem started, I have been in panic mode and may have done something stupid I just chose to subconsciously block out

After I flushed the problem plants, I did give them a dose ('bout a gallon each) of epsom salts, maybe a 1 1/2 tsp per gallon. This I did because of another potential problem I am seeing, with yellow tops (I created a thread about that too, but got 0 replies: Worried parent - Are my plants OK?). But this was After the browning problem had already started.

It also just now occurs to me, and makes me wonder about the PH down I use - its DIY using Car Battery Acid (Sulphuric acid). But its the same stuff (or similar) used in commercial PH Down, so who knows.
But I am still not convinced it's a sulphur problem, and if it is, what to do next?

I guess I will now just have to try flushing the affected plants again and hope for the best. Flushing is a major chore for me, as my site has no running water and I have to haul it in from my house in buckets, PH it, and add it to a pair of 20 gal garbage cans - takes a long time. This is extremely frustrating, since aside from this browning problem, and maybe the yellow flowers, the plants look great. Anyway if you can maybe think of a "plan B", it would be greatly appreciated. I don't want to lose my girls.

BTW checked out a few of your threads, good stuff.

 

[Droopydroors]

Just going to throw this out there because it happened to me. My pH meter is cheap and I have caught it a few times being waaayyyyy off so I had to calibrate it. I'm sure you have but just making sure.

 

[unkied]

Hey Droopy!

Funny you should mention it. I am definitely a Cheap pH meter owner. I originally purchased a VantaKool meter (off Amazon) that seemed a bit wonky - kept deviating - stick it in - get 4.8, swirl it around - get 6.5, rinse repeat. I noticed that the solid probe seemed to have "gunk" on it, so of course I scraped it off with my fingernail. Didn't seem to fix anything, so what do I do? Of course BOUGHT ANOTHER IDENTICAL one. Turns out the "gunk" was actually a protective coating FYI it's this one:

Anywhoo, it seems to behave a bit better than it's predecessor, but that aside, both came with calibration stuff, so I did calibrate both of them. Then I compared. Then re-calibrated, then calibrated again. At present, both seem to lock in at about 6.83 and 4.01, give or take 0.02. So as practice I use BOTH of them when checking PH. And calibrate every other day. Both meters clock my pH at between 6.3 and 6.45, depending on how patient I am with my pH adjustment regimen.

I do also have a cheapo soil test kit. Put soil in tube, add fluid, push thru filter, dump in test tube, add reagent, look at chart. My pH test with that showed LOW pH, maybe in high 4 to mid 5. But then again, the color didn't really match ANYTHING on their chart, so who knows. So I guess 2 meters vs 1 cheap test kit, the meters trump the test kit. Further, with that cheapo test kit, I put in brand new, virgin Fox Farm Ocean Forest, and it showed Depleted Nitrogen, abundant Phosphorus, 0 Potassium. I then treated that soil with pure 0-0-17 Maxicrop seaweed powder, let it dry, tested it, and got back 0 Potassium. I chucked the kit.

Any way, thanks for the input, and maybe you're still right. I hate to own three of these meters, and can't really see/find any better rated quality meter (at least that I can afford).

 

[Droopydroors]

Ya sounds like you have it covered!!! I think I have the same meter but mine is yellow. I calibrate it before mixing up my nutes once a week. Just figured I would mention it and I was hoping that it was the issue because then we would have had an easy fix!! I'll keep my eyes open while I'm trolling through the forums and let you know if I see anything. Have a good evening and I hope a solution comes to you soon!