Flowering issues

[kunkgrow]

Hello friends,

I'm desperate can't take this shit anymore!
This is my 4th round and every single time when I reach 4th week of flowering shit starts to go downhill.
Everything seems on point.
I have no clue what happens.

Check the pics, the bulge begins to halt and leafs necrose and die.
This is sad.

Nute is only 1.3ec, PH 6.0 on point, temperatures always ok.
Last round the room was 100% sealed with CO2 and I read about sealed room phantom issues, so I decided to vent every hour even though it increased my CO2 expense. Thought it would be ok, but nah, same outcome.

Substrate is Sphagnum/Perlite 50/50.
Watering once a day until runoff, containers 7L.
Lighitng is 2x Fusion Boards for a total of 150w only. So can't be light stress.
CO2 was running at 900ppm, but at first sign of issues I left at ambient (350 to 400) to no avail.
runoff = 5,3ph 1,0ec

feed regime:
Jacks 321
RO Water.

Only known issues:
Some bugs on the soil, looks like gnats, they're so small I cant catch them or photograph them. Not huge infestation, maybe some kind of bath fly. Can't be sure, however what I know is last round they were not present but the issues were the same, so can't blame these bugs for the current outcome.

I'm out of ideas. Need help!

[Hyakutak]

I think 7 liters pots for such bigs plants is far from enough. You probably need something like 30-50 liters pots. And you need to let the soil dry sometimes. Watering every day is probably too much & is probably not helping with the bugs infestation.

My 2 cents, not an expert.

[Sativant]

I think you may be overwatering them. Thus the gnats. Don't water them everyday. Bigger pots would help a lot. It's very hard to get the watering right when plants are pot bound.

[DaveJonesFan]

If the potting mix is really only peat and perlite you should consider adding some actual nutrition to the soil IMO.

1/3 of that should be nice fresh organic material like leaf mold compost or fungal dominated compost. You can also add some organic fertilization beyond that with something simple ilke easy to find Jobes mixes or Dr Earth or Alaska or what I use, Espoma brand. Your mix should ideally have some pH buffering as well. I use some Garden lime.

Big pots with organic fertilization can stay in the ideal moisture window longer and help you keep your use of the jack's to lower levels. I use (18) 7 gallon pots in a 4'x8' with peat based soil mix.

Going straight peat mix and pumping 1.3 ec into it at every watering, and having to water frequently is a recipe for this sort of lockout if not straight into overfertilization if you are not keeping everything cascading perfectly so as to keep moisture and pH and nutrient levels ideal. I have no idea how your runoff would stay lower than your input as any peat based material I've used builds up salts with fertilization at every water. Peat may even require flushing throughout flowering if you are really favoring the salts.

If you want to stick with straight hydro nutrient feeding, look into more peat specific recommendations. A lot of people use rockwools, coco coir, or straight dwc types of methods with greater success with the specific methodologies you are employing.

[kunkgrow]

Thanks for all comments mates.
I will let it go and use what’s left for extracts.
Next round I’m gonna try different medium, maybe Rockwool cubes are best for my automated setup.

I chose small pots because I thought I could water multiple times a day and it would be great.
Watering once a day til runoff is barely enough, they’re dry by the end of the 12h period.

I don’t know how FloraFlex does it with their 6inch pots, huge plants on such small containers flowering till the end .

[DaveJonesFan]

Yeah it's spot on the water stress then if you are going bone dry to soaked every 12 hours.

Can you adjust the automated watering to finish these off? Try less water every 6 hours or some variation to keep moisture levels from hitting full soak and desert dry so frequently. You want as much time in the middle of those extremes as you can get. Water can only really be automated when you know the parameters of what it needs.

[psyduck]

Your LED is burnig them, you just have to pull it up. monochromatic light have to be at least 60cm form the top of the plants in the flowering.

[H0m3B0Y]

To me your plants look similar to this one:

Here is a quite from the web page I found it:

Pink leaves, red discoloration, rusty spots and edges… While it make look like these cannabis seedlings are experiencing nutrient deficiencies, all these symptoms are actually caused by a combination of overwatering plus a too-small pot.

When the roots aren’t happy, the plant isn’t able to uptake nutrients properly and cannabis seedlings can show a wide variety of strange problems.

Like other said: give 'em bigger pots, feed them a bit less. You'll easily see if/when you underwater them. Underwatering causes less damage (unless you're keeping them bone dry for long periods) and it's much easier to give them some more water than to repair drowning/rotting plant.

[unkle_psycho]

It seems to me you are using a strategy normally used in coco? Smart pots would prevent roots bounding, no idea how spahgnum (is that peat?) reacts to continous nutes? Does it release all elements equally with runoff?

The buds still seem to be fine, damage mainly on fan leaves.

[Tickles the ɯılʞɯɐu]

Run off PH 5.3? Nute lock out? and/or maybe Salt build up.

If your putting 6.0 but run off is 5.3, chances are medium has lower PH and the 5.3 is read after being buffered up with 6.0

Id either flush through til PH is close to going in as it is coming out, or you could up the PH going in over a few feeds til the run off gets to 5.8 or there abouts.

If the PH is causing lock out, then its easy to think your plant is deficient and start pumping more nutes in. Where in reality, drop the nutes, get PH buffered correctly in the medium with straight water.

Let the medium dry between feeds/watering to allow oxygen to the roots otherwise good chance of root-rot.

Also, with LED i always add 1-3ml of cal-mag per gallon.

Pests?

Sprintails? Fairly harmless, not a concern.
Thrips? You got a problem.
Fungus gnats? You got a problem.