Not enough light. Unless you grow tiny plants in small pots and flip to 12/12 right away. I think maybe 2 at the most under a 150 with no additional lighting. Something will always suffer if you try to over do it.Talk to me, how does that sound. I know it's not great but it's what I'm working with right now. One auto in flower under that came out amazing. I got 6 regs that are short and stout that I want to flip.
I think in got 2 males. But still if yield is going to be poor with the 150 I'm not gonna do it. If you look at the pic I trained the shit out of themIDK. I re read your OP and since they are regulars you might get 3 males. Like dude said, you can get away with 3 fems under a 150 but yield will most likely suffer. It's kinda like YA gotta match the whole system and desired results. more plants, more watts. More watts more fans for the heat. Etc.
They look good bro. No doubt. I'm mostly a 1 or 2 plant guy and have a 150 and it's great for that. But, I do supplement with 109 watts of LED. More is better, but a 400 or higher HID would just be overkill and wasting electricity for me. A 250 would prolly be good for 2 or 3 plants. Anyway, I'm surprised others didn't chime I. For you on this subject. A lot of HID guys on RIUI think in got 2 males. But still if yield is going to be poor with the 150 I'm not gonna do it. If you look at the pic I trained the shit out of them