Of course I already do all of this.You might want to raise your light some, if your starting water only she's not going to need that intense of light to just mature up. Also try to keep temps below 85F if you can.
I pay a lot of attention to all of the parameters you wrote ( light distance, temp etc...).
I have a 600w hps laying at 53/54 cm from the main colas.
Temp is 24oC now and it has been like that all over the grow.
Sometimes the problem i face is low RH.
As Waira said that could have been the issue.
As u suggested me I would like to let her mature for about a week with just water, but i'm afraid of those leaves coming out from the calyxes.