My first grow in my life (G13, Amnesia Haze Auto, White Widow XXL)

Excellence The G13 couldn't shed the seed coat during plant growth, so this was done manually. I had problems with my light, which caused the plants to stretch, but they're still salvageable. Since I pre-fertilized the soil and moistened it with fertilizer again during planting, I've only been watering with water since then.

Excellence The plants were repotted into 15l fabric pots and watered with 2l of nutrient mix each.

Excellence Last night I installed a DIY CO2 system, but I could barely measure any CO2. I'm sure gas is leaking and circulating in the box, but the desired dosage of over 1200ppm seems unreachable for me :D Day 17: I suspect, also due to the measurements, that this might have nothing to do with adding CO2, but today I noticed significant growth compared to yesterday. Currently, the plants are growing horizontally. So far, I've been watering every 3 days; today would actually be watering day again, but since the soil, according to measurements, contains plenty of moisture, I'll skip it today and postpone it until tomorrow. I think it's time to start training, and I'm currently getting informed through videos. What do you think, when and which method(s) should I apply? On day 20, LST was applied to the G13 and White Widow. Leaves and shoots that weren't getting light were cut off. The Amnesia Haze Auto was topped, and leaves were removed here as well. Thanks in advance for the helpful comments.

Excellence Today, the plants were stretched further. I notice that the ladies are stressed and currently gaining very little growth. That's why I will leave them alone for the next few days :D The bottom of the pot is almost wet, I'm considering sticking to the 3-day rhythm but watering with 1 liter instead of 2. Alternatively, I could go with 2 liters over 5 days, but I don't know how dry it will get in the middle or above the pot. How do you keep your soil pleasantly moist?