Howdy webanator. What are the water and air temperatures? Also are the reservoirs (planters, buckets, or totes well aeriated and all of the possible light leaks (no clear tubing or uncovered holes in the lids or covers)? Have You been changing out the nutrient mix regularly and topping off (at mid-week with pH'ed water? And the 'big' question, is there a musty smell in the reservoirs? Root rot (brown algae) can cause many problems for the plants that can resemble various nutrient deficiencies. I try to keep the water temperature between 61° F and below 70° F, and the air temperature should be kept below 85° F.
Good luck with Your grow.