Promix issues

[Jonnysact]

Hey family,

haven't posted on here in a while because things have been going pretty good. But here it goes:

Strain: Phoenix Sun
Medium: Promix BX + perlite
Water: Tap @ 140ppm
Feed: GH Flora Nova Bloom (lucas's formula)
Temperature: 76-77
Humidity: 40-55

Waterings happen every 3-4 days @ 7.4 or 7.3 for a runoff of 6.6 - 6.7. Feed at 450 - 500 ppm. Water until runoff every time.

It looks to me like I'm getting a Mag deficiency with the rust spots and the purple stems. Lime new growth and slow growth. This is exactly the issue I had with my previous grow until user Chimera helped me fix what was wrong. My runoff was far too low causing lockout. I flushed the medium until it was able to get a runoff more appropriate to what the medium required for optimal uptake.

Link to that thread: https://www.icmag.com/ic/showthread.php?t=323514

Now... I should still be in the sweet spot of uptake. Watering at 7.4 for a runoff of 6.6. The ONLY thing I can think of is that I need to flush my medium to raise it's PH slightly, but then part of me thinks that my runoff is still hitting my target number but I'm still suffering from what looks like a low PH. Ideas?

Thank you guys!

 

[TheScrogFrog]

I have never fed in Pro-mix with that high of a pH. Been using Pro-mix for almost 8 years.

I feed between 6.0-6.4.

Why do you think raising your pH above 7.4 will benefit you?

Far as I know -- Iron, and Manganese can get locked out above 6.4-6.5. Anyways, not sure what your issue is, because I rarely ever have any issues, but curious why you are feeding at such a high pH?

Is it possible your pH is too high and you're locking out Manganese?

Exhibit C looks a lot like your lower leaves.

 

[Jonnysact]

Thanks Scrog Frog. the link in my thread will explain why i'm at that ph.

The skinny version from user Chimera: "Water at a pH no lower than 6.7. Even then, over a couple of weeks, you will see the pH of the effluent/run off will drop. You want the pH of the medium to be 6.3-6.7 after all is said and done. If you are watering at 6.7 and the pH of the effluent is coming out below 6.3, you are heading for trouble again.

Ensure you ALWAYS have 15-20% runoff from the bottom of the pot. This will stop nutrient buildup which causes the pH to crash, which is locking out Mg and causing your plant to suffer."

 

[misterD]

I used pro mix for two decades, and i could def told you. Give some cal/mag!

 

[Mikell]

Run off is not a good indicator of anything.

A slurry test is.

Try a few pots at 7.0 and some at 6.0-6.5.

 

[morningdewd]

I used lucas formula with pro mix when I ran out of HR V and B and plants suffered from nutrient lock out in about one week. they looked very similar not as bad I caught it early. IMHO Lucas formula is way too strong and out of balance for pro mix. I see you run at 500 ppm .I cut the Lucas to half strength and still had issues . I think its better suited for rockwool. MD

 

[G.O. Joe]

Yes the formula was not right for me either in promix. A straight grow formula at 450 with no pH adjustment should work out IF extra limestone is added to the mix, dolomite is preferred. That's the best calmag and pH control for promix. The tap water here is like 8.5 though so I either neutralize or use RO or distilled water never even tried a nute pH higher than 6. What has the ppm of the runoff been?

 

[Jonnysact]

Most recent runoff was 450ppm.

 

[AeroKush102]

I have never experienced any problems with Promix as far as the plants are concerned. The BX works right out of the bag. Flora Nova may be the problem. I've used that line for hydro and Promix and was never completely satisfied with either. I normally use Botanical Grow 20ml Cal/Mag or Cali/Magic @10ml and would surprise them with some Fish Emulsions or Seaweed at 10ml when I had extra money to play with. It always worked for me, never a burn or a bad ph problem, hell I stop using my ph meter for years afterwards.

 

[G.O. Joe]

Promix has limestone in it already but it needs a cup per cubic foot more. With near-neutral water and GH or Botanicare nutes it's been totally possible to not adjust pH ever for perlite/vermiculite, promix, and rockwool grows.

 

[Scrappy-doo]

I never added any lime to promix and always fed at 6.3-6.5 when I was using bottle nutes. Never had a problem. Imo 7.3 is way way way too high. Ridiculously high even. Those rust spots are a sign your ph is off. Promix is near flawless right outta the bag. Don't fuck with it just feed @the right ph and ya can't go wrong.

 

[Jonnysact]

Thanks guys, I'll flush my plants and try to bring up my medium's ph, then try feeding at a lower PH and see how things go from there. Will also supplement with botanicare cal mag.

Will report back when there is progress to report!