Does it look like nutrient deficiency?

Looks like classic nitrogen deficiency. I learned with my DWC though, that when it gets bad, your best bet is to do a complete res change. Always remember to measure your EC every day or two. Dropping EC means you can increase nutes, raising EC means to decrease nutes (or in your case, top off with pH'd water). Your pH is good at least, but remember to calibrate your meter if things just don't seem right. Its a good idea to get some test strips just to verify that your pH meter is accurate.