PH Dropping daily, Leaf Discoloration

I'm starting to have an issue with the ph dropping in one of my res. I usually run steady at 5.7 but recently when lights come on in the morning and I do my morning rounds the ph in one of the res is dropping to 5.1 to 5.3 . I flushed with plain ph'd water 2 days ago for a few hours and the ph stayed right at 5.7 and didn't fluctuate. So I drained that water filled back up and added a lighter nute dose than usual (around 750ppm usually around 1400ppm this late in flower). The nutes I run are the botanicare pb bloom, sweet, karma, and now in the later weeks FF Cha Ching also. The roots all seem to fine, at least the ones I can see as I cannot pull out the bigger plants this late as all the roots grow together and around the internal plumbing inside the tubes and they don't budge unless you want to rip up a bunch of roots, but the tons that grow right into the res from the drains are nice and white and they stay submerged. I started to think root rot cuz that always seems to lower the ph as well, but as I say I see no bad roots. Some leaves are starting to show signs of a def (looks like mag) but that is expected with the ph getting so low. The overall health of the plants seems good, the younger ones seem to be going great but the older ones on the right seem to be starting to stall and they all drink from the same res. I'm at a loss as to why the ph is dropping at that rate and am trying to head off a potential problem, any Ideas? first pics are of the worst leaves and then a couple of group shots to show the general health of the plants.

Also there is a single Critical Sensi Star that is in with these plants and it shows no signs of any problems at all, which is weird to me because they all drink from the same res. Any thoughts?

Anyone? Bueller... Bueller, is this thing on?

this must be a tough one huh.

how are you growing, in bubblers or something? you say roots are growing through the rez to the drains. what does that mean? how big is your rez? are you recirculating?

I am running 18 gallon res with a homemade aeroponic set up off the SB design, with the 4" fence post covers and the ez clone sprayers inside, with a 1min on 4 min off cycle. The roots always grow into the res, that is usual, the weird part is the ph drop. As I type right now I am flushing again with pure water and clearex because again this morning the ph is at 5.1 when last night before lights out it was 5.7 . I wouldn't really care this close to harvest but like a moron I didn't fill the system at once this time, I put 6 in then a week or so later 6 more then a couple more a week after that, and this system sucks for trying something like that because the roots grow around everything especially the internal plumbing and each others roots making it almost impossible to remove plants without ripping & tearing the roots all to hell. so I'm trying to figure this out without having to try a full on intervention and remove all the plants and bleach the whole system like in between harvest and the re insert plants that would suffer tons of damage from the roots being molested, but if that's where I'm at oh well.

so your rez is 18 gallons. how many plants feeding out of that? with an 18 gallon rez, 4 plants is about your max. if you have a bunch of plants feeding out of a rez that is too small, you'll see wild ph swings. 5 gallons per plant will keep ph pretty stable.

wow! 5 gal per plant would put me at a 70 gallon res. This is not the first time this system has ran and I have never had this problem before. I don't know if you've ever seen the Stink Bud setup elsewhere on this site (https://www.rollitup.org/hydroponics-aeroponics/116859-harvest-pound-every-three-weeks.html) but this is about identical. You can see that many many people are using this with the 18 gal res with no issues as well I have never had any issues either. The identical system sitting right next to this one is running along fine with the same amount of plants and the ph has been rock steady as usual. I am concerned this is some type of fungus or something although I have yet to find any slimy roots or the like. Thanks for the suggestions though, it is appreciated. Some folks just like to spout quotes from books and magazines but when it comes to a real issue that they can't quote out of a book or use epsom salts or molasses to fix the room goes silent, so like I say thanks for your input I appreciate every tidbit of info anyone can give me.

are the plants in the other system the same strain? you may just have some heavy feeders/drinkers.

All are the same except 1, take a look at my grow journal in my sig. This has really got me scratching my head as I am no botanist. I guess tommorow I may try some hydrogen peroxide in the flush and see what happens.

sounds like bacteria or algae in the res.... the ph drop is indictive of there waste/by products... urea= nitrates= acidic= low ph

IAm5toned said:

sounds like bacteria or algae in the res.... the ph drop is indictive of there waste/by products... urea= nitrates= acidic= low ph

Click to expand...

Thanks, that's what I was leaning torward. Is there a way to get rid of it without removing all the plants?

you really shouldn't respond to a problem until you determine what it is. once you see a symptom, go from there. i looked at your journal, and i'm still leaning to rez too small, lol. i know, i know, but hey, what else could it be? 18 plants in 18 gallons is a lot of roots to feed. plus, if that tub is 18 gallons, i doubt if it's filled up to the top. that would make your rez even smaller...... (scratching head!!!)

it's 14 plants but I understand the theory, I usually fill it with about 17gal. After these ladies finish up I will up to a 25gal or so depending on what I have room for. I've read that the more water the more stable it is, I've just never had a problem so I just left it. I'm gonna go dump the flush water and scrup the entire res down real good and fill it back up and see what happens. I think I may just run plain ph'd water for a few days, this pouring nutes down the drain is gettin expensive!

i hear that! even cheap nutes get expensive if you have to dump them. keep us updated.

Cleaned the entire res, wiped everything down real good twice. The city must be helpin everyone out as the water is streamin out of the tap at 5.9 ph so I'm just gonna let it pump that plain water through for a day and see what happens in the morning. Thanks for the help!

Looks like IAm5toned had the right idea, after the scrub down and flush the ph seems to be levelling off. I never had any issues before this with anything happening in the res so I never thought to scrub it down with the water change but will from here on out regardless. Thanks for the help, ones in front have a couple weeks the ones in back a couple days, Thanks again!