Problem with young plants in DWC

I'm currently growing 2 plants in dwc and 4 in coco, both 17.5l, (think different and bulk smash) equal splits between the plants. PH has been between 5.5. and 6, room temperature has been 22.1 highest 19.1 lowest (teperature outside is about freezing at the moment). Plants are on 24 hour light, which i keep them on for 3 weeks before switching to 20/4

Plants are 13 days old, the plants in DWC's first set of single point leaves began to curl/warp and bend. Accompanying this was greyish green dark patches on the affected leaves. Initial thought was 600hps too closse at around about 20 inches from the plants. Not sure however, as this has affected the two strains in DWC, and none of the strains in Coco - the DWC pots are about 2 inches higher however, and i top my DWC pots with white and black + an insulative layer to preven light getting to the res through the hydrotron, and to keep the res temps down, which might mean higher light intensity for the girls in DWC.

3 days on and this hasn't spread any higher on the plants, but the affected leaves have become quite/very (in bthe case of the bulk smash auto) brittle. Anyone able co confirm my suspicions that this is a light intensity problem or is there something else going on?

My nutes accross the board are: Per 17.5l

Dutch pro A+B 10ml each
Dutch pro take root 5ml
Black liquid humate 5ml
Pythoff at 1ml (redosed every 4 days)
Power thrive at 5ml, (redosed evey 4 days)

Cheers.

I would go with the light being too intense. Lift it up higher until you find the sweet spot. I would normally hang a 600w at least 24-30 inches above canopy and see how you go. Start with 30 and lower if or when necessary....?

Cheers for the response. Light intensity was my initial thought, but then why lower leaves first, and why only in the DWC plants, fred on the exact same nutrients? Seems odd.

My light, a cool tube has hot spots. I have about 4 spots where the light seems to be more intense in certain places. I could get a new/different shade but when I lifted it from 18 up to 24 inches away from the canopy my leaves stopped bleaching. It was only a few that got bleached but enough to put the girls under stress...

Probably need the light a lot higher as they are so young as a 600w will be too strong at this stage of growth

I have had strains running side by side before and sometimes some strains can't handle strong light intensity as well as others.

Yeah, it wasn't light intensity, it was a defficiency. Switched nutes. Plants in DWC almost dead now ha.