Looks like calcium deficiency to me. Never had it though. Pics below are calcium deficiency. What kind of water are you using?
Nutrient lockout would be caused by a buildup of Fertilizer salts in your soil, or a ph problem with your medium. If its salt buildup it would be fixed by runing a bunch of pure phd water through your soil, enough that you get plenty of run off, next time it dries out,(dont water early over this, adding overwatering wont help) then let it sit for a few minutes so the salts absorb into the water and then run more water through to wash it out. If its ph issues you have to adjust either the ph of your soil or your water if your working in some type of soilless or hydro. Waters good to adjust either way of course but in soil the ph of the soil itself is more important.
A ph meter a very important tool in any growroom. There are specific ones for soil instead of liquids