Well, Its recommended to give the Girls 18 Hours of Light. But I personally see no Problem of giving them less.
Iam growing previously autoflowers outdoor, and they get 12.5 hours daylight, and they still grow and build flowers.
As you are using aHigh quality light, with a big DLI_ output, It should be the lessest Problem for them
P.s Your Girls looking alittle pale... maybe its the Light in the Pictures... how do they look alive=?