just started flowering

two days ago i flipped to 12/12 yesterday everything was fine, some of the preflowers on one of the known females were getting bigger even after 12 hours, i wake up today and go to look and all look good except the tallest, its top growth was like u-turned 3 inches and looking straight at the ground. the whole bent part of the stem was floppy as hell. i just staked it up and got the top growth as straight as possible. they just got fed yesterday morning and the soil is still moist. i also bought a ph meter the other day but i think its just a piece of shit. i put it in the ground down to the roots and wait 30 seconds like it says and its still on 7. maybe it is seven but there was no fluctuation at all between all six plants, they all read exact seven. its running out of 1000w hps with very good air circulation, the tall one is about a foot and some inches away from the light so im raising that immediately just incase, but its not even hot when i hold my hand there. any ideas anyone? this was top 2 of the healthiest ones...