i'm no expert. i'm experiencing my first grow now. my plants are about 18in tall now, and despite some grower error, they are doing well, i think. i'm sure it will be safe to grow these sprouts a little bigger before transplanting. the cups are transparent though. that's not good because light is bad for roots. if you see roots through the cup, transplant into dark solid colored pots. use pots at least 10 cm tall. i transplanted mine when they had 4 or 5 leaf sets.

i never learned to use metric measurements, but i read that ideal temp is about 80 degrees Fareinheit. cannabis will grow in temperatures from about 60-90F, i think.

you can smoke male plants, but because males have very low thc levels, most growers don't waste time growing them. also, a male plant will fertilize nearby females causing seeding. by eliminating males, female plants will grow seedless buds. it is likely that one out of your three plants will be a female. whether you should grow more at this time depends on how much time and money your willing to spend on your project and how much space you have to dedicate to it. you will have to nurse the plants to flowering to determine their sex or make a clone and rush it to flower. 12 plants occupy considerable space in a controlled environment and require regular attention.