Ya I'm growing in my basement right now so the temp is like 15-20°C would aHello retnuh I am a new grower so heed my advice carefully just my opinion, seems to me like you for sure over watered, stress and root issues = slow growth, also dont water when the top "looks fairly dry" dig a finger gently about two inches into soil, if it's moist fall back and be patient, if its dry ....water, it is better to under water then to over water, over watering can great life long problems or even death from root rot and under watering is easily solved by... Watering lol also I would note your stems purple.... Which to me says Your grow temperature is to low in my opinion. So guys what do you think of my advice?
I actually have a heater fan that I could probably use to heat up the room and maybe blow wind near the seedling but I'm not sure if it's a good idea to have hot air blowing by so should I just use it to heat up the room? Or to blow cold air near the plant?well, the finger thing probably isn't a good idea in a solo cup. it's better to pick up the pot and see how light it is. make a point to feel the weight of it when you're putting soil (or coco or promix or w/e) in it dry. you don't want it to get that light, obviously, but closer than you might think.
it is better to underwater than over water, but it's best to water the right amount. that depends on what kind of medium you're growing in, how vigorous the plant is, what the temps, RH and airflow in the room are.
as far as the purple stem, it say its mostly genetic, but cold roots (from being wet all the time) could be contributing to it.
didn't think to mention this earlier, either. if you have a fan in your tent, don't have it blowing directly on your plant. its much better to aim it at the wall behind the plants and let the backwash hit them.
I've got 2 40w 5000k fluorescent t12 set about 4-5 inches away from them but I don't have any way of accurately knowing the temp any suggestions or should I just not worry about itI'd keep it at the lowest if possible 75° ...might lower the light and see how warm it is after the adjustment... depending on what light u have going