I should have asked you guys for help

I messed up temperature and humidity and killed/stunted my plants.
I have a small closet grow space 2x4x6.
I've been growing autos in soil with decent success since last spring. A couple of months ago when temperatures started to drop I started having issues with slow growth and what seemed to be nutrient deficiencies.
I fixed my central heating system and trying to keep heat in the house most of the time.
I had the lights on 18/6 (lights off 11pm), turned off the heating around the same time because the house holds heat pretty well for a few hours.
I have no ventilation system really. A desk fan in the grow space and I would open the windows a couple of times a day and open the closet door to change the air. I haven't been doing this much the last few weeks and I've just been reading about its importance for temperature and humidity control. I also don't have any way of measuring them at the moment.
I'm thinking if I start some new seeds, put the lights on 24/0 for one crop, hoping this will keep temperatures and humidity more constant.
I was pretty disappointed when the nicest plant I've vegged so far just started to die. I was going to give up until spring but I'm feeling a bit more optimistic today.
I know if I asked for help, I probably would have saved it.
The last pic is how it looked a few weeks ago. It was getting darker green despite not giving it much nitrogen.

Keep the door open, or figure out a way to circulate the air in and out. Plants need fresh air constantly.

Cut a hole in the door put a 4" intake fan in it , put a 4" exhaust and filter up above and vent into roof space , have them on a twin speed controller set at desired temps .
Bit of £££ but worth it in the long run IF ya continue to grow .

Trickyticky said:

Cut a hole in the door put a 4" intake fan in it , put a 4" exhaust and filter up above and vent into roof space , have them on a twin speed controller set at desired temps .
Bit of £££ but worth it in the long run IF ya continue to grow .

Click to expand...

Thanks for the reply. I will definitely try to make that happen. In the process of germinating some seeds now. I'm gonna try 24/0 and put a wet towel in there. I'll have to just make sure I keep changing the air lots of times each day.
The benefits of being home all the time

Haha , well if ya wanting to save cash ya can just put hole in door with bug proof vent have carbon filter as passive intake .
Another idea .