Hey mate! For the tiny light that you’re working with these plants are doing astonishingly good!
I’m just confused as to why you’re using CO2. It’s a total waste in your case and there’s no need for it. CO2 only helps if you’re growing within very tightly controlled parameters and with A LOT of light and way higher temperatures. Seeing as you’re using a 40W light and your temps are nearly too low, the CO2 you’re adding could actually hurt your plants more than it’ll benefit them.
I’d suggest to remove CO2 entirely until you got very high temps and a powerful proper light.
Happy growing!
like