how can it be that my plants, when they are about 15 to 20 days old, become almost dry in the stem so they break? is my light too weak? I'm really sure about that, it's like it can just support them at the beginning and then they die off.
your humidity levels might be very low causing the stems to dry out
in a pinch you can put a wet towel in the tent to help raise the RH a bit
good luck mate
