Deficiency?

It's the start of something, but depends on recent behaviour and things like pH. if you can rule out ocd and other craziness and the pH is good... yeah, i'd feel safe at saying something is deficient. Can't believe i'm going to say it twice.. looks like a Ca deficiency -- they are rarely actually ca or mg def in most contexts. If you are heavy feeder, think about easing back for a second or re-evaluating your concentrations and ratios of nutes. if it's pH issues, get that in check first and easy off on nutes.. since in flower maybe not water-only in this perticular context... a TDS meter can help, but it's fairly inaccurate... if it's crazy high, that's beyond the inaccuracy in some cases. rule out hte easy stuff and increase Ca a bit if none of it tracks. Ca deficiency actually start long before you see them. you can likely stop the spread, but it may not heal much between now and the end. Also, as long as slow enough, it shouldn't cuase too much of a problem. If any concern about exactly what it is, be conservative and wait and see a bit, with a water-only irrigation or 3 for fun. change that up as you observe reaction.