Nutrient Deficiency???

Good question. With out knowing the EC/PPM of the feed its hard to say. Some plants eat more some less and a lot of the definiteness can look like excess at time. Over all its looking good in some photos but others quite yellow. Hard to tell whats the real colour. Looking at your diary it looks to have been showing a bit of this since starting flower. Monitoring your runoff EC and PH will confirm it does not have a built up of salts in the soil that's causing lockout and will confirm if it is hungry and needs more. When the top leaves yellow first vs the bottom, its a sign its not always nutrition they need, and it could be less of something. The purple blushing on top could also be a bit of Stress from the lights or it got a bit cold in the tent at night, not the main problem though should not worry to much about it. Your going to see a lot of advice but until you know the numbers ec/ppm/ph of the solution going in to the plant and the run off coming out, it is going to be a guessing game. I highly suggest you find this info out before committing to a plan of action. Happy Growing!