Your plants are looking really good brother, please dont get antsy and chop them early. You will be rewarded with much more potent smoke if you let it go for an extra week or even two before you start a 7 day flush.
With your bagseed looking very sativa dominant, i would give it about 65-70 days of flower before you flush for about 7 days.. remember that the first, at least week or so before you actually start to see pre-flowers, this time should not be considered into flowering time as the plant is changing the hormones being released to trigger the plant to start to reproduce (grow buds). Thats why breeder times are always off a bit.
like STOP said, take a breeders flowering time and add, i would say, 2 weeks to be safe. Sometimes one extra week isn't enough, that second extra week could make all the difference in really good smoke, or top shelf quality buds.
You're on the home stretch now, and while it ma be tempting to get to smoking that lovely plant, the more patient you are with it, the more rewarding the end product will be for you..
When you are ready for harvesting, i made a recent blog post on how to prepare your buds for the drying room, check it out if you want some good pointers!