I will update how much I fed the plants later. This week was grazy, one plant grew a lot, the other is somehow blocked...
This week started well, Plant 1 nearly doubled in size in one week. I turned the lights a bit higher, but the plants did not like it so much.
One night I messed up with the exhaust fan, and for 5 hours the plants were staying under 32 degrees. Plant 2 that was not gorwing much leaped within this time. But later I read that this is normal for cannabis plants, and that is not really healthy.
@Maryjane23, Thanks!
I do not know why the plants grew so compact. Mine look quite different than other Orions I saw. I wonder if I should turn my lights into a lower setting. Any suggestions?
Day 10: Added 0.75 g ammonium nitrate and 1.25g of magnesium sulphate/L and irrigated both plants with 1L. The second pair of leaves started to show
Day 12: The second pair of leaves developed.
Day 13: Added 1ml/L BioGrow and 0.5g/L of magnesium sulphate. Today I can see that the third pair of leaves developing.