Ca deficiency from low pH?

[4d-Rock]

Problem: lower leaves getting blotchy yellow/brown patches. Also drooping of leaves

Medium/grow method: 50% pro-mix seed starter (peat moss/coco mix), 25% organic top soil,25% perlite. Indoor space bucket grow.

Feed: and supplements used: only water up until now

water source: tap water which comes from a lake gets filtered through carbon and UV. PH is about 6

Strain/age:white widow auto flower fem - 22 days

light used: 3x 10Watt Led 3000K bulbs with 1x 10Watt led 5700K bulb

Climate: day ~ 22-24 deg C, night ~19-20 deg C, hum 50-70%

Additional info: started to think the drooping was originally an overwatering issue, though it still could have been, but the lower leaves started to discolour brown and yellow. After watering tonight the runoff had a pH of ~5 ( low accuracy strips is all I have). Was wondering if I should be doing a flush. Don't have pH up at the moment, unfortunately, so I may have to resort to baking soda if that's the case until I can get some

Thanks!

 

[Autoflower420]

Ph 6 is a little low for soil need to be about 6.5

Sent from my SM-G930F using Tapatalk

 

[namvet25]

No need to flush yet but raise your ph up with baking soda if thats all you have.You can also start a mild veg feed at this point.

 

[4d-Rock]

Ok thanks for the tips. I won't go full flush. Since I've just watered it what should be my plan of action? Wait it out to dry, use corrected pH and mild nutes on next watering and hope this doesn't get much worse in the meantime? Or is there something else I can do now?

 

[Waira]

-- looks like a little P defc. on those leaves,... pH related likely at that reading,.. yeah, you need to adjust the pH, after you're added the nutes... your water looks very soft at 6.0, low mineral content; feeds are acidic too, what are you using? ....... you need proper gear mate, no way around it,... aquarium dropper test kits for pH are at least 0.2+/- resolution, close enough,... baking soda is not a good choice, for long at least, it has Na (Sodium) in it, which is toxic to cannabis at low levels,.. there is a potassium carbonate equivalent, for milder control,... or just get some pH up.... adding a Ca-Mg product will help as well,...** oops! I mean mildew control-

 

[4d-Rock]

Thanks, I appreciate the recommendations Waira.

I ended up doing an additional 1L of 7.0 pH water after that last feeding to hopefully lessen the effects of the acidity until the next watering. I also propped up the smart pot in front of the fan and periodically ran a dehumidifier to help dry things out quicker to prevent serious overwatering.
It's actually not doing too badly, the lower leaves are still looking bad, but likely they won't be fixed, the damage is done. But the rest of the plant is looking decent and still growing (I've posted a pic below).

I have some more accurate pH testing strips on the way that have increments of 0.2 to help pin down the measurements. I'm using a diluted, general purpose garden fert from Pro-mix, it's strong at 20-8-8, but I've been doing like 1/16 tsp per 1L to start (and have only done one feed so far). And I know baking soda isn't ideal for a long term solution, I'm trying to source some pH up locally but I think I'm going to bite the bullet and buy some pH up and CAliMAgic online. I still also need flowering nutes so if I get all these at once the shipping will be a bit more reasonable.

 

[Waira]

oof! 20-8-8, even dilute, that's way too N heavy, and low on P-K and other secondary + micronutes,... when you dilute so much to compensate for one nute element, you short yourself on the rest,... general purpose is just that, a shotgun blast that may work for most plants, but cannabis culture is a different game,... point is, there's more potential for deficiencies when doing this,.. if you look at the N-P-K ratios on other typical grow and bloom nutes, you'll see what I mean,...

 

[Rev. Green Genes]

oof! 20-8-8, even dilute, that's way too N heavy, and low on P-K and other secondary + micronutes,... when you dilute so much to compensate for one nute element, you short yourself on the rest,... general purpose is just that, a shotgun blast that may work for most plants, but cannabis culture is a different game,... point is, there's more potential for deficiencies when doing this,.. if you look at the N-P-K ratios on other typical grow and bloom nutes, you'll see what I mean,...

I had to science that up a bit.... just cause I'm that nerd that won't shut up about it! I was shown this way back when. It refers to the 'law of the minimum' where you fix one deficiency, and the plant is then limited by another. Like the water in this barrel which is an analog for yield, and each barrel stave is for a limiting factor. As you fix one, the next deficiency presents as a limiting factor.

 

[4d-Rock]

I get what you guys are saying. In hindsight it would have been better to just order online all the specialized feeds to begin with. Rather than working with what I had locally.

So then you'd recommend discontinuing the use of those nutes? Here's a couple recent shots. Still getting growth, but definitely still droopy. Last pic is an attempt at leaf tucking to get some light on the lower nodes.
I've also raised my bulbs, realized they might be too close as well, about 6-8". Now they are more like 20". And I'm leaving it an extra day or so before next watering to prevent overwatering. Should have my CalMag and pH plus by then as well.

 

[4d-Rock]

Hey @Waira , I've received my ph up, calmag, and I also included tiger bloom in the order. The pot is fairly light and the surface soil is slightly damp, not quite dry all the way. I also havent gotten a replacement yet for veg nutes.

Additionally to what I said above, what recommended course of action should I take?
I was thinking a pH corrected watering with just calmag to start. Maybe just a small feed and not to runoff to see how she reacts. But if it's a nute deficiency then maybe I should feed as well. Though on this front people usually say less is more.

Any thoughts?

Thanks

Also FYI, I've attached a pic of the full analysis of the nutes I used (only one feed done up til now)