Looks like nute burn at the tips and a deficiency of something where the rust colored spots are. I had a similar thing happen before, wish I could remember what the cure was. Good luck. There's a good guide to plant problems on GrowWeedEasy.
The technique itself seems to be problematic.. You can't run a decent DWC with soil. the soil zone will be flooded AF and the plant will die. The root zone in the DWC basket ( with clay pebbles ) should stay dry when the roots zone are well developed. A good way to start seeds or clones in DWC is to run them in soil for the start and then wash the roots zone and transfert in 100% clay pebbles.