Branches stretching and poor flower production - 400W DWC

Hi fellow growers.
I have kind if an embarasing problem on my grow.
I had this system setup in the attic of my previous home (~1 year ago), so I know the system is working, but something is clearly not right.

Current system:
Located in a camping trailer.
70L container DWC SCROG.
Locally bought liquid organic garden nutes + BioBizz Bloom.
Lots of air through ceramic airstones. Powerfull centralized air pump, running several containers.
400W HPS light on 12/12 cycle positioned ~20cm from top of plants.
2 x 36cfm exaust fans (a little on the small side, I know).
Ph around 5.4-6.0 (using electronic Ph measurer)
Humidity 50-70%
Water temp. 22-24C
Air temp.25-28C
Mixed strains: K19(?)xHaze and Original Haze.

Problem:
Most of the branches that should now have been fatty colas, are thin stretching thingies. They are still stretching after 7 weeks of flowering,and only a few female flowers. Please see pictures.

Propable causes:
Heat stress (though I don't experience any burnt leaves). I have not currently any fans blowing over the tops.
To little air circulation in the trailer.
2 times of accident with me forgetting to turn off working light in dark period.
Maybe I have stressed the plants by training branches allready in flowering.
Instable Ph. I have to correctthe Ph every day. It keeps climbing from~5.5 to ~6.4 every day. Don't know why.

Extra info:
I have 7 plants in the container, and some of them where kind of big when I placed them in the container. They where transplanted from soil and where used as mother plants grown from seeds, so they have been through som stess in their life.
All foliage looks super fine with healty green color. All roots looks healty too.
My last and first indoor grow, in the attic in my previous home, I grew Skunk #1, and I know the Haze is a totally different beast.

Third attached picture is of the whole screen. I know there is WAY to many big plants for that little space, but it's hard to chup these ladies down, you know . And as I mentioned, these where almost all mother plants, preflowered under a 150W HPS, that grew a little wild when I had to have my brother in law take care of them when I was 14 days in France. I just coulden't stand not putting the mother plants to some work, but maybe I should just chop them down, and start over with some clones to get smaller plants, even hight and a more controlllable setup.

Any input would be very much appriciated.

Thanks!

your heat stress is probably the main cause of your stretching and bio bizz are primarily soil nutes mate, it can be run in drippers(but not advised) and its unstable in dwc, flood and drain etc because its of its organic structure it breaks down fairly rapidly in the res and this will be causing your ph fluctuations, ive been using bio bizz for 6 years now in soil and you always have to mix up your nutes/water fresh, made up solution should be used within 24hours, and adjusting the ph of bio bizz nute solution is a no no too, ph adjusting acids will lock out the nutes, and a ph of 5.4-6 is far to low for bio bizz, your probably locking out allsorts hence no bud after 7 weeks of 12/12, when you add bio bizz nutes to tap water they normally bring the water ph to 6.4-6.5 and this is around the optimal nutient availability ph for bio bizz. if you wana grow organic in hydro look into bio sevia nutes theyre hydro specific organic nutes, and it does well in dwc. so in short id say beef up your extraction and swap nutes and raise your light a little, 200mm is just a little close for a 400 in an open reflector.

Londoner said:

your heat stress is probably the main cause of your stretching and bio bizz are primarily soil nutes mate, it can be run in drippers(but not advised) and its unstable in dwc, flood and drain etc because its of its organic structure it breaks down fairly rapidly in the res and this will be causing your ph fluctuations, ive been using bio bizz for 6 years now in soil and you always have to mix up your nutes/water fresh, made up solution should be used within 24hours, and adjusting the ph of bio bizz nute solution is a no no too, ph adjusting acids will lock out the nutes, and a ph of 5.4-6 is far to low for bio bizz, your probably locking out allsorts hence no bud after 7 weeks of 12/12, when you add bio bizz nutes to tap water they normally bring the water ph to 6.4-6.5 and this is around the optimal nutient availability ph for bio bizz. if you wana grow organic in hydro look into bio sevia nutes theyre hydro specific organic nutes, and it does well in dwc. so in short id say beef up your extraction and swap nutes and raise your light a little, 200mm is just a little close for a 400 in an open reflector.

Click to expand...

Thanks a lot mate.
I raised the lamps yesterday, and today it allready looks a bit better. The stretching seems to have stoped or at least slown down.
I know that bio bizz is for soil, but thought that it would do OK in hydro too, but if thats the reason why my Ph fluctates, I think I better leave it.
I'll order some Advanced Hydroponics stuff, though it's not organic, just to se the difference and have something to compare with. I'm getting tired of ajusting Ph every day, and if it also locks up nutes from my bio bizz, whats the point anyway.
I'm looking forward to getting som clones started in the system, and start some serious growing.

SwinG said:

Thanks a lot mate.
I raised the lamps yesterday, and today it allready looks a bit better. The stretching seems to have stoped or at least slown down.
I know that bio bizz is for soil, but thought that it would do OK in hydro too, but if thats the reason why my Ph fluctates, I think I better leave it.
I'll order some Advanced Hydroponics stuff, though it's not organic, just to se the difference and have something to compare with. I'm getting tired of ajusting Ph every day, and if it also locks up nutes from my bio bizz, whats the point anyway.
I'm looking forward to getting som clones started in the system, and start some serious growing.

Click to expand...

if you really wana go organic why not grow in organic soil? no need to adjust ph ever, no need to test feed strength with meters? harder to get things wrong? or use that bio sevia grow and bloom 100% organic and designed for hydro, its been getting some good write ups?