It's hard to properly diagnose problems without colour. Purple LEDs hide most of the signs we need to pick out problems. But, it certainly looks like it's low on nutrients overall
I had the same problem on my last grow. I just plucked all the dead ones whenever they showed up and the buds turned out fine. It didn't really seem to effect the plant all together. I couldn't really find a diagnosis for it but I just figured since it happened so late in flower that the plant is basically utilizing the nutrients that the leaves had either stored or were using. That's all I could come up with because the plant had no other symptoms or slow of growth. Sent from my Pixel 2 XL using Grasscity Forum mobile app
exactly what happened.! Og4201's plants are doing the same thing, there is a bit of nitrogen shortage and the plant is using the N that the fan leaves had stored in them. my master plan is to have most of the fan leaves looking N deficient at the end of flower and still have half or more on the plant.