Looks fine to me. I see what your talking about. Could just be that the plant is sucking something from the leaves its not getting in the soil. Which is fine as long as it doesnt progress too much. I really like the shape of your leaves. You have only a few burnt tips so I wouldnt think it was over nuting, and they are not yellowing really as it appears in the pics so I wouldnt really think it was a ph problem with nutlock or something. Start with your water and the run off water for ph. The flush was a good Idea. I think u should be fine. Kinda a nice looking hue haha.