flushing confusion need help

I have 3 WW females each 13wks old(7 weeks into flowering). They share a single 3gal hydro bucket. Two of the plants appear to be in the same stage of flowering and are nearing the time to be flushed. the third one looks to be about 3 weeks behind for some reason. It just took longer to develop for some reason. my question is whether i should start flushing now or wait until the 3rd plant is ready?

i say keep flushing. harvest what's ready when it's ready, then hit the late one with flowing nutes for a week, then flush again for two. (you said three weeks behind, right?)

If the third plant seems worth it move it to another bucket. If not don't worry about it.