purple leaf tips

Ok, so this might not actually be a problem, not really sure. But anyway, two clones in hydro have purple-ish leaf tips on the new leaves. The roots haven't yet reached the water (they're in DWC) so maybe they're slightly starved for nutes? But the stems are green, so I'm not sure. It's NLXBB, so it's not a purple strain.

Any input? It's still persisting, it looks kinda cool and they're still growing. I'm keeping the nute levels pretty low still, not willing to up the nutes too much yet as they're still young.