90% sure this Mg deficiency, but a second set of eyes would help please.

[Ro0k]

UPDATE:

So when I chose coco as a media, I did so because I didn't want to go full hydro, but I wasn't keen on either building or buying soil (I don't want bugs and stuff in my garden). I also wanted to be able to control as many variables as I could while learning how this plant grows until I get more experienced and gain enough confidence to start screwing around with it on my own. I've watered it as I would soil, and other than this issue, it seems to be working for me. Water, wait a couple of days till the media dries a bit, water again.

So what I did to remedy this was crank the lights back a couple of inches, and stop using regular water every other watering. I re-calibrated my EC and pH pens as well, and added calmag for the last week or so. The plant seems to have recovered somewhat. Obviously I won't 'heal' the yellowed parts, and they've turned brown, but the plants overall seem healthy.

• After a week of remedying, and watering with nutes, the EC coming out of the pot is ~1300.
• pH is around 6.3 coming out, so that's a bit on the high end, but I'll get some pH down to fix that.
• I still want to flush with regular water every now and then to keep the EC down in the runoff, but I'll back that up to once a month.

I've only got about 4 weeks left in the grow, and it looks like I didn't kill the plant, which is a good thing. Assuming I don't crash and burn on the home stretch, I think I've remedied the problem. Plants aren't any worse, and still growing nicely. I've got some nice colas forming:

 

[Roger A. Shrubber]

more than likely is Mag. coco is notorious for eating magnesium, till it fills it's "deficit", then it immediately becomes much more available. a lot of people will have trouble, as they've become used to adding it each time, when the deficit gets filled, they keep adding it, and then have an overabundance, which causes as many, if not more, problems than a deficiency

 

[Ro0k]

more than likely is Mag. coco is notorious for eating magnesium, till it fills it's "deficit", then it immediately becomes much more available. a lot of people will have trouble, as they've become used to adding it each time, when the deficit gets filled, they keep adding it, and then have an overabundance, which causes as many, if not more, problems than a deficiency

Yeah, I've read that. Like, you don't need to constantly add calmag to coco since it's a micronutrient and isn't needed in huge amounts. I'm going to back off on the calmag this week and next, because I don't want the calcium to cause other lockouts. When it comes to nutrients, I'm a big fan of the 'less is more' philosophy. Keep 'em alive, but always go for the low dose when given the option. It's easier to add nutrients to fix problems than it is to remove them.

 

[polishpollack]

Doesn't 1300 coming out seem kind of high? Are those leaves too dark green? I'm wondering if this is more of an over fert problem than anything. How does coco eat mg? Why would calcium cause lockout? Are you referring to the pH? I don't think 6.3 is so bad.

 

[Ro0k]

Doesn't 1300 coming out seem kind of high? Are those leaves too dark green? I'm wondering if this is more of an over fert problem than anything. How does coco eat mg? Why would calcium cause lockout? Are you referring to the pH? I don't think 6.3 is so bad.

I hope it's not nute burn. I'm using the coco light schedule on the canna site, so it shouldn't be. Though blueberry is a finnicky feeder. The plants seem to have recovered and are doing well. Though I think I will flush for 10 days instead of a week this time. The pics below were snapped on nov 15, and the plants seem to have recovered and are healthy and growing wild.

 

[mr_c]

Let me point you to a site that wants NO money....
https://cocoforcannabis.com/

BOOM - there it is again!