Nutrients problem maybe? Light shades of green started coming in last few days gave it few days to darken up as I know new growth is light green I did split main stem few days ago could that be a reason for this ?
Maybe...they will recover. just don't tweak anymore and keep an eye on watering too much at this stage. they are streessed. Also, maybe, they are gettingo into flowering stage. Cannabis become clearer green at center when they are about to flower.