4 plants, 1 week into flower

So I started 4 plants flowering last week by their own request (Two were showing quite a few obvious female pre-flowers). Now the two that were showing the pre-flowers are starting to reveal themselves in all their feminine glory, however the two that weren't producing pre-flowers I still haven't been able to sex yet.

Here's the catch, the two obvious females are the two with genetics I KNOW I want to keep, and the two that haven't shown signs yet are two I was growing basically just to get the hang of it since this was my first time from seed and not clones.

Would it be wise to just scratch the two I don't care as much about so that the two of good genetics can't possibly get pollinated should a male show up, or should I leave them a little longer just to make sure neither of the other two are female. When do the male pre-flowers begin to really show themselves and after how many weeks flowering is pollination a concern?

I would keep at least one of them until you know it is male or you can smoke it. Who knows? It may just be the best smoke you have ever had. If so, then revert it and make it a mother. Usually males show up about the same time females do, sometimes a little later. I've had males dropping pollen within 1 month of flowering.

Good advice. I kept them all alive and it didn't take more than another 3-4 days to figure out which were which. Killed one male, and all the females are packing on bud like nobody's business. I'll start taking pictures around week 4-5.

Good news on the extra female the patience bit is hard but you just got a nice dividend from it. Look forward to seeing the pics.