Should I be worried? Yellow leaves

A little die back aorund the base of the plant is nothing to crazy, I would not be worried about this. One thing I would be worried about is that you are Feeding liquid nutrients and I hope you are getting some runoff with your feedings to help prevent a buildup of salts in the medium. When you don't get runoff the salts build up and cause some other issues like lockouts from too high of an EC in the root zone and PH issues. I have noticed your using AN as your nutrients, that brand tends to feed heavy so you buy more of their product, I'm not a personal fan of their line up, so pricey and other options out there for much less that do all the same stuff if not better. Maybe look into this once your done your current lineup. Also look into getting EC pen to confirm your feed concentration. I did not see any EC/PPM readings on your diary, It could be to high and you might want to make the nutrients last longer by using less of them. Good Luck!