The light was too close. So I raised it at 1m .
I made an other mistake, again : I applied the nutrient mesurment for 2L and not for 1L.... and one has been over watered. So I removed water from the tray and decide to stop watering her for 1 week.
The leaf on 2 of the girls seems to be a bit burned by light. It's because of the too close light but it should be ok now...