Heat stress? Controlling water temp in hydro

[mtgshmoopy]

Hi everyone.

Currently growing a Sweet Mango auto (Greenhouse Seeds). I haven't been doing good recordkeeping but I think it's around 8 weeks in. Here's some info:

pH: ~6.6
air temp: 74-76F
water temp: 72-78F
nutrients: GH trio, CalMag, Hydroguard
light: Electric Sky ES300 (running it at about half strength) https://thegreensunshineco.com/produ...00-grow-light/

As you can see in the photos (ignoring my sad spinach seedlings), I've got some rough yellowing, crisping, and curling. The landscape oriented photo is from the 16th and the other is today (25th). I haven't done any sort of intelligent trimming but every few days I pick off the dead leaves that come off if you so much as touch them. Usually get a small handful of leaves each time. Leaves all over the plant die, not just near the top or just new growth, and my roots look great which leads me to think it's heat stress. I'm currently putting frozen water bottles in the reservoir to keep the temps down (otherwise the reservoir will get up to 80-83F) but I struggle to switch them out in a timely manner because of my work resulting in the wider range of water temps I listed above.

I haven't gotten out my cheap usb microscope yet but judging by the pistils sticking out so much I'm guessing the plant still needs a few more weeks before harvesting (I try to harvest before any amber trichomes show up). What worries me is the progression of the dying leaves.

Any advice is appreciated!

[DW2]

Howdy mtgshmoopy, It looks ,to me, to be nutrient deficiency caused by too high of a pH level. The pH level should be at 6.0 (+/- .05) so that the plant can properly absorb the nutrients. Keeping the level around 6.0 will allow a better absorption of the nutrients. I do not use the Hydro guard, I keep the root rot (brown algae) under control by using ice bottles, keeping the water temperature between 62° F and 70° F, keeping the water well aerated (four 4 in x 2 in air stones in each reservoir), and by blocking out all light leaks by covering up the net pots with aluminum foil.

[mtgshmoopy]

Hey! You're the one I got the ice bottle technique from when I did my first grow last year! Love to see you still making the rounds spreading your knowledge =).

I got my pH range wrong... I thought it was 6-7 in the bubbleponics tutorial on here but reading it again I see it's 5.5-6.5. Dang! I'll change out my reservoir and keep it around 6 as you suggest.

Thanks!

[DW2]

Thanks for the kind comment. That's one of the things that I like about growing in hydroponics, when things go bad or get out of hand, You can just drain it and start over. I also had a problem on my earlier grows, trying to 'chase' the pH during the grow. I almost killed off several plants. Now I just pH adjust the water (to 6.0), add the nutriments, and then do a final adjustment to bring it back to 6.0. I let the pH fluctuate as the nutriments are taken up by the plants and my grows have gone better since I 'quit the pH case'.
Good luck with Your growing.