Plants look pretty good, maybe a little stretched, and IMO should be bigger with that light at that age. That light looks really far away for a 400w, but I understand that temps are an issue. What are the temps in there? Have you tried moving the light down, or tested with your hand to see what's bearable for the plants? I'd also mount the light sideways instead of hanging...

I think your next move should be to find a way to cool that light and your room. High temps will slow growth and flowering and could cause harmful stress.

BTW - CO2 is only effective in a sealed room.

Happy growing :jointsmile: