Slow growing

Spoiler: Quick info

Strain: White Widow
Plant type: Clones
Tent temperature: 31-32c (house is 28c so I can't really change that, heat wave right now)
Water temperature: 15c-26c (I use ice packs/ice bottles to cool it down so it swings a bit)
Water PH: 5.6-6.0 (usually 5.8, I always dose to 5.6 because it swings back up)
Water Nutrients: 3:3:3 GH Flora (6.25ml in 10 liters) with a pinch of epsom salt
Water change interval: 2 weeks
Lighting: 2x 300w Mars Hydro pulling 250w at the wall (replacing this with 4 high power cobs soon)

I'm growing White Widow and this is my first time experimenting with DWC. My first grow was in soil and it took with this particular strain 6 months from seed to harvest. I planted late July and harvested in January.
I have built my DWC system with 10 liter buckets which I painted black first to block light, then painted white to reflect heat. I have a bubble stone in each bucket. I started my grow in soil out back of my house, grew a mother plant from seed and took 2 clones from it which I am using in my system. At first the clones didn't do much for about a week, no new root growth and no leaf growth. In-fact the plant slightly yellowed. But now its kicking back into life (I believe they were in shock from transplanting soil to DWC). Loads of new roots and foliage is developing but its going quite slow compare to growing in soil. I regulate my water temps with bottles of ice and try to keep it anywhere between 15c (after adding ice packs/bottles) and 26c (by the time I got to change them which is 2-3 times a day). It swings back and fourth as bottles melt and I put new ones in. I am running a 3:3:3 mix of General Hydroponics flora series at 6.25 ml per 10 liters and a pinch of epsom salt. Ph swings between 5.6 up to 6.0 and I dose it down again (usually 5.8). My house temperature is 27-28c right now because of a heat wave so my tent temperature is 30-32c. I keep a tray of water in there evaporating to raise humidity.

Anyone know why my plants are growing so slowly? Its been 2-3 weeks since the new growth started and so far they are growing really slow compared to when I was in soil. I switched to DWC because I thought it would be a little faster.

I'll attach some pics below:
IN THIS PICTURE THE LID IS LIFTED WHICH IS WHY THE ROOTS ARE OUT OF WATER.

YOU CAN SEE HERE THE OLD YELLOWING LEAF FROM THE CLONE AND ABOVE THE NEW HEALTHY FOLIAGE. (There is some tip burn, not sure why)

THIS IS MY SECOND PLANT IN THE TENT, THE NEW GROWTH HAS A LEATHERY APPEARANCE IN PLACES.

 

UPDATE: They appear to be speeding up in growth and look a lot healthier now. My second plant is starting to get brown sludge on the tips of its roots. I think there is some pyth developing in there so I have bought some pythoff to treat it. Trying to keep on top of my water temps as much as I can. I think its about time I start thinking about changing my system to one with an external reservoir outside my tent. I'm thinking a bulkhead fitting at the bottom of my reservoir will feed water into my DWC buckets via gravity. Then a small fish pump on the return line will draw water back up from my second bucket and dump it back into the reservoir. I feel like having the water flowing outside of my tent into a cooler room will drop the temps by a degree or two. Plus having the air pump outside the tent should improve thermals inside too. With a recirculating system it also opens up the possibility to put an aquarium chiller in series with the loop if I get enough money or find one cheap enough. Also a UV sterilizer in series probably wouldn't hurt to keep bacteria levels down in the water.

 

I have a pump and two large air stone pumping loads of air in. Its so difficult to regular temps right now. Since the weather is so hot right now, my grow tent is really hot. And the water just heats and heats. And the ice bottles cool the water down a fair bit. I'll try and manage it even better so it stays around 20. I was unaware that 15c was too cold. Thanks for the info.

 

Right now my temperatures drop a decent amount during the night, I'm almost certain if I can hook up an external reservoir then the increased thermal mass will keep the temperatures more stable. Plus I can throw frozen bottles of water into an external reservoir much easier than my buckets where they mess with the roots. Its finding the right fittings that are tricky. I know I need bulkhead fittings but they are a huge pain to find online. Apparently putting a towel over the bucket helps to because it insulates it keeping the hot air out and the cool air in. Going to try it tomorrow.

 

Okay I just dosed them with Pythoff now to kill the root rot. 0.2ml/l every 4 weeks keeps root rot away according to them. But since I change my nutrient solution every 2 weeks I guess i'll just half that dose to and apply it twice as often. So I'm quite happy about that. Since last night my plants have EXPLODED. Literally doubled in size. I just topped them. They have very tight node spacing though so I raised my lights a bit, I'd like them to stretch a little. I may have accidently over done the PH a bit, its down at like 5.4 right now.... oops. I can't really add any more water so I'll let it rise naturally. It should hit 5.6 by tonight which is the safe zone. Hopefully back to 5.8 tomorrow. It was 6.5 when I measured it earlier.

 

How long do you have from seed to harvest? I just upgraded my light big time so hopefully I get better growth. But my plants are growing super slow right now. But my white widow outside is fast as hell.

 

I upgraded to a Mars Hydro Pro 2, the top model 320 led. Pulls over 700w from the wall on max power. Should be plenty
But I think I know why my plants are being stunted. My nutrient was way too weak, I looked up a nutrient chart for the GH flora series and i've doubled my strength now

 

I have Canna rhizotonic, good stuff

 

Yeah canna is pretty good stuff indeed, albeit quite expensive. Maybe i'll try it some day. Right now i'm good with GH Flora series