15L vs 5L

@GreenCosmos, Sorry for the late reply. You can already see a noticeable difference. The 5L plant is significantly smaller and has fewer bud sites. I think it's due to the lifting soil, which is just not enough to support the plant for more growth. In this case, root bounding exists, but with mineral fertilizers and proper application, it shouldn't matter for the plant's nutrition; you just have to water more often since the substrate can hold less. In my case, where the substrate provides the nutrients, it's clear that with too little substrate, the nutrient supply is too tight.

@GreenCosmos, the size of the pot is relatively unimportant since it's all about nutrient supply. The bigger the pot, the more secure you are with nutrient supply because the roots can access everything in the pot. In smaller pots, they rely on you. For autos, a 20L Airpot is recommended. Seed banks suggest 15-35L. In a years-long test in the USA with some strains in 3 large tents, it was said that 12.5L is significantly more challenging than 20L, and more than that is usually not necessary. Additionally, 4 plants/m² with 350W LED, for example, an Evo5 Sanlight. The most important points can only be implemented favorably in larger spaces. So pay attention to light, nutrients, soil, and ideally in a bedroom or office due to CO2, air movement, and temperatures between 20-25, max 16-30°C. Fungi and bacteria help with feeding in the soil.

@GanjaBoy84, Basically, the air pressure ratio is more important than keeping the temperature down (some people would probably disagree with me, but I haven't had any problems even with temperatures up to 31 degrees). So I do it this way: when the temperatures rise, I adjust the humidity. Mold shouldn't form at those high temperatures anyway.