I notice that the leaves are very dry and curl up more and more. They are also very dark green. I use a small fan 24/7, 18 hours of light and the lamp at 45cm. What could be the cause of This and what can i do about it? Thanks in advance!!
Your humidity and light placement all look fine and so does your growth honestly. That canopy color looks ideal as well. Might have dried out a bit too much at one point but I wouldnt worry about it as the plants look like they are doing great atm.
After topping its quite normal to have some leaf mutation here and there its nothing to worry about. As the other grower has stated the plants look very healthy I would not worry about it. Keep up the great work. 👊