I would say that it looks like N deficiency but usually the plant consumes the leaves, eg they shrivel up starting at the tips of the effected leaves. The flip side is that if it were bleaching it would be on the top leaves closest to the light. The issue doesn't seem to be isolated to one plant but the one has it worse than the others. Am I correct so far? I would guess that it is N deficiency, in the case that they all share the same reservoir and others have the the same issue to lesser degree, I would call it that. Is the one that is almost all yellow a different variety? Either way I would hesitate to increase the nutrient solution by too much but a little would be ok. You could do a light foliar with N supplement to isolate the individual, keeping it only on the leaves. The response should be quick, hydro is fast and foliar feeding is fastest. I haven't used lucas formula before so I am unfamiliar there, but it looks like depending on your nute line you could be low on N. Many strains like a steady flow even in flower.