They don't really look like the SLW pullets I've had, but I've only had a few so I'm nowhere near an expert. I'd be curious to see what they look like when they're grown.
They're looking pullet-y to me, though.
If you're only culling due to gender, I'd wait a little longer so you can be certain. I like to harvest around 10-12 weeks for tasty meat.
From your pics, I'm only confident that the black one is a cockerel. I agree that the splash is probably a pullet. For the other 2, maybe try to get some...