Hand watered hydro?
eek.

You gotta flush your medium out real well. You've got symptoms of a serious burn/lockout problem, but your ppms are too low for good growth. Where did you get the gravel from, and how did you prep it for use?

You also need to be adding calmag with tap water that soft. I don't know the Dutch MAsters line at all, but in flower you should be able to run 1000ppm ferts EASILY without burning, so either your medium is to blame or your fertilizer isn't right for your system. Also that pic is very blurry and if you can get clearer ones of the damage, plus a couple of your overall setup showing a whole plant at least, plus proximity to lights, that would be great.