This is DWC - check your pH first and foremost. Next, check the airstones in the reservoir - are they clogged or is the water getting enough oxygen?

Change water weekly. Some don't change and just top off nutes.

Don't use plain water, just make sure your nutrients are properly mixed and balanced, and you should have no overfeeding issues. Use plain water for the last week of flowering to help flush out a bit (if that's your preferred thing.)

Usually, the curling upwards leaf ridges and the slight ram-horning of the tips hints at a magnesium or calcium issue.