High!
I'm a new RDWC grower. I'm growing auto flowers this round. I'm in my second month and my girls are flowering. Everything was going great the last two weeks. All the sudden this week after a nute change things went out of range. I am having huge pH swings over the course of 4-6 hours I'm seeing my pH go from 5.6 to 7.4! The EC had stayed constant. Last night, I lowered my EC to try and help what looked like nute burn on one plant. This morning my pH was 7.6 and EC bumped to almost 1200 ppm. I was running my EC up to 1000 ppm with the nutes I'm using. I lowered it last night to 775 to try and help the plant that was burnt.
I've tried draining and cleaning my tanks and doing a complete reset with my nutes. I've about lost my mind with this pH fluctuation. I have damn near gone through an entire quart of pH down in the last 4 days!
I've calibrated my pH meter and verified it was working. I'm out of ideas.
I do not have a tank cooler but I'm running at 68-70 degrees. I also have bubblers in each tank and a recirculating pump. I started running hydrogaurd at 2 ml per gallon here this last run. That was my only change. Room is temp controlled to 68 - 75. I have an exhaust fan and circulation fan. Humidity runs 50 - 55.
I have a Torus pH perfect on it's way but it won't get here for several days...
Any suggestions is greatly appreciated!!
This is the pic of the droopy girl. The rest look fine..
@ghscgrower EC fluctuations can be a bitch to get hold of in hydro man, dont worry it happens 
My gues would be, that you have added PK recently,. and that really fuck with the pH of the water.
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― Mark Twain
First the disclaimer, ima coco grower so no direct experience with rdwc but I can offer a guide that deals with EC and ph fluctuations. The stretch is done and it sounds like your girls are looking at a different diet now. There’s a chart in that article that deals with the problems you are describing. Hope this helps a little.
https://percysgrowroom.com/ec-and-ph-fluctuations-in-hydroponics/
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So I've come to some conclusions. I switched my pH down and added hydrogaurd recently. I am getting more pH down like I was using before and going to do another res change again. Fourth since Saturday. I'm going to re add nutes to the range I was using prior and go from there.
Thanks for the suggestions!
Please say something if I missed something obvious here. Thanks!!!!
@ghscgrower hey man, like monkey I'm a coco guy and not any experance in dwc, but I was having issues last grow and figured out my ph down was organic(citric base) which isn't all that stable over time,once I switch to a pg down with phosphoric acid I had no issues so thought I d share , hope you work out what causing it for your sanity more than anything by the sound of it lol, happy growing
Thanks guys! Hopefully everyone has had good holidays! I finally got this under raps. I switched back to the pH down I had been using and scraped the new stuff I tried... My pH and EC swings stopped. Thank F!!
I do still have one girl that's unhappy. She has been having yellowing leaves. I'm guessing that it likely is a lack of phosphorus? I am raising my pH range up to 6.0 - 6.2 since they are in later stage flowering now. Will try this... I did add more PK to the latest nutes. I'll likely be draining and replacing nutes here this weekend.
Any other suggestions?
GSHC good job mate👍
Wait and see the effects of adding more pk and getting your pH back in check.. the lower leaves are pale where nutrients are mobile within plant so plant is naturally cannibalising or simply using some stored food in lower leaves which it no longer needs. Top growth is healthy so just monitor and keep pH and EC in check.
I do RDWC also. " Ice probe" works great also put res in separate room from grow light:),
Be constant with the hydroguard, water temps 68-69, No light leaks. It sounds like you had a bacterial bloom, more like a BOOM!
Keep ph high6.2- 6.3 so cal/mag will be available in flower.
Shoot low Boyz, their ridin Shetland ponies.
The Hydroguard has saved many a grow for me. I use it throughout every grow religiously
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