Wondering if this is a pH issue or a deficiency? Started at lower leaves now starting towards the middle, advice on what to do is appreciated

For soil I always pH at 6.3, I wouldn't remove those leaves yet, keep them and watch them to get worse or stop getting worse. If you cut them off the plant will start pulling nutrients from other leaves. I'm not 100% what's wrong with your plant but I had a similar problem, I increased micro nutrients and cal mag and it stopped. Again it looks kind of the same but it could be different. I suggest upping your ppm a little bit, and adding a little Epsom Salt to your water or nutrients. I use a tsp for 3 gallons and it works miracles. If that's the problem it will be recovered in 10 days or less. Sorry I couldn't offer better information