Daily light intake. The girls can only handle so much total light for the day. Once they receive that amount they do not want to do any more photosynthesis.
I noticed when running my QBs at 60 percent on an 18/6 schedule my plants looked excellent in the morning. Praying to the light, everything perfect. 4 hours or more before the end of the day cycle the plants would point their leaves down. This would be normal activity if it were almost lights out but not 4 hours before hand. I reduced the light percentage down until the plants would pray for all 18 hours.
I run 4 x QB 132 3500k (300watts) in my 4x3. During veg plants don’t need much light. I have the light at two To three feet and turned down to around 30%. So the plants are getting a decent amount of light for 18 hours. When we go to flower and reduce the schedule to 12 hours of light the plants now need more light over less time. If you have been running your boards at high power it is not possible to give them this increased DLI unless you add more lighting.
TLDR. Turn down your an a lot. Raise it to 3 feet. Seedlings don’t need that amount of light. Begging plants don’t need as muchlight as flower but they have more hours to get it.