looks like they could swell some more to me, flowering times are just a rough estimate and usualy on the short side. every new grower wants a plant that will flower as soon as possable. so the shorter the date, the more desirable it is.
you can chop a plant when it has 80% brown/red hairs, you will get a racy high, if you leave it to mature those extra few weeks, you will get a nice sleepyish high, due to the CBN content. it realy is down to you.
if you need convincing, cut a small bud now, dry and smoke, leave the rest of the plant for those extra 2 -3 weeks or more, dry and try that, you will notice a plesant differance in high.