Yellowing top leaves 5 or so weeks into flowering. 1000w dwc. (pics)

I'm kinda new to this, and I'm not doing too good at figuring out this problem on my own. Can anyone help?

This batch is Nirvana Blackjack. I'm currently running rdwc...5 gallon buckets with a 1000w HPS. The tent is just about 4"x4". The bulb is aircooled, because in the beginning it made my tent REALLY hott. Now it's pretty good...it goes up to about 82 or 83 degrees at the most. I checked all the obvious things like pH and PPM levels. My pH is pretty steadily locked in at around 5.8 or 5.9. I'm using Advanced Nutrients 3 part pH perfect. It's no joke...it doesn't really need to be checked that often. I'm also using advanced nutrients hobbyist pack, so that adds a few additives to the mix. I change the solution once every week and a half or two weeks. The PPM bounces around 800-900. I'm probably about 5 or so weeks into flowering? Not really sure exactly because I haven't been keeping track. According to the website this strain goes for 9 or so weeks. I'm concerned about some of the top leaves turning yellow. It almost looks like a deficiency of some sort, but looking at the charts its hard to tell (for me at least). It could also be heat stress. Any thoughts? The 1000w is actually pretty close to the plants....maybe 8 or 9 inches? But with the air cooled hood it doesn't really get hot, even if the plant was touching the glass. And it only seems to affect certain parts, not the entire top of the canopy. I posted pics in hopes there was something I was missing.

Thanks in advance!

Kinda looks like a Mag or Zinc deficiency.I would bump up nute strength just a little bit or use Epsom's salts starting at 1/4 tsp per gal.
To be safe you can raise the light a little instead to let the plant balance itself out as you further troubleshoot.
(more light= more nute uptake)

i would say raise your light

I don't really have much room to move the light up. I guess Ill try tying them down a bit to give some clearance. I foliar fed them with Epsom salt. I also added a bit of Earth juice microblast because it has both magnesium and zinc in it, among others. Let's see how this goes.

Mg deficiency........fairly early, imo.

Pic 1 looks like copper def

K(potassium) deficiency with the singed tips. the yellow going inward looks like zink deficiency, it might be a ph thing or probably a hungry plant issue

Are you adding your nutrients to R/O water, or tap water ?
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If you are using tap water, mineral levels can rise and fall like a rollercoaster, from week to week. Some of the minerals present in tap water will bind with others (like Nitrogen) locking them out, even though they are present in abundant amounts. The quality of your water is just as important, as any other factor, when growing hydro.
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When in doubt, dump, flush and refill (with a different water source *, if not R/O water). If you're feeding 800 ppm, above your water ppm's, that should be more than enough.
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Two additional questions, when was the last time you checked the calibration on your TDS & pH pens ? Because sometimes, them numbers just aren't right.....
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* R/O water from a fill it yourself station, or bottled 5 gallon distilled water jugs. Both available at most chain grocery stores. Kroger, Wal-Mart, etc....
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Yea, I'm thinking it's the hungry plant, lol. My ph stays pretty rock solid since switching to the advanced nutrients ph perfect. But I've only been doing about half strength because I was told that full strength is too much. Im due for a nutrient change here shortly so maybe I'll up to 3/4 strength and see what happens

I'm using RO water. The PPM is almost zero before adding nutrients. When I add all the nutrients at half strength, the PPM will be around 800-900ish.

I calibrated both about 2 months ago. They weren't that far off when I did. I'll check them again.

Gtds420.... Sounds like you've got it handled then. If both pens are within parameters, I'd dump, flush, & refill using a different nutrient source. That way you can rule out, wheter or not you got a bad bottle of nutes (expired, sludged up, too acidic or too alkaline). It happens, even with name brands.
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One issue I am running into is the size of the roots. I'm using dwc, but I have them recirculating through four buckets and a 20 gallon reservoir. The buckets are 5 gallons. The roots in one of the 4 buckets are really big, and causing the bucket to overflow! The roots are blocking the return line so it's not draining as fast as it should. Because of that, I have the pumps on a timer. It turns on and off every 15 minutes. Maybe since the roots arent getting submerged in water and nutrients 24/7 its hungry? I'll have to try and fashion some kind of overflow line so it's not an issue and I can run the pumps 24/7.

I raised the light last night as much as I can, and changed out the nutrients.

gtds420 said:

One issue I am running into is the size of the roots. I'm using dwc, but I have them recirculating through four buckets and a 20 gallon reservoir. The buckets are 5 gallons. The roots in one of the 4 buckets are really big, and causing the bucket to overflow! The roots are blocking the return line so it's not draining as fast as it should. Because of that, I have the pumps on a timer. It turns on and off every 15 minutes. Maybe since the roots arent getting submerged in water and nutrients 24/7 its hungry? I'll have to try and fashion some kind of overflow line so it's not an issue and I can run the pumps 24/7.

I raised the light last night as much as I can, and changed out the nutrients.

Click to expand...

I'm experiencing a similar problem with my rDWC system where my 3.2 gallon buckets are so packed with roots that the water level is rising too high for comfort. I put my pump on a similar time schedule to allow time to drain back to reservoir as well.

Have you figured out a better solution yet?

Really sucks because I'm just about finishing up the third week of flowering on an 8+ week flowering strain. I've got a long road ahead.