So, 8 days after germination, all seedlings are feeling fine.
Temperature is dropping slowly but I've added a 3rd old led lamp which added 3-4 C and now daily temperature is about 27-28 C.
Humidifier was turned on and currently showing values around 50%
Update about the growbag size - it is 3 gal each, around 11 liters. The bags are ready and I water them periodically to let the soil sink in order to add more soil before transplanting.