Problems while flowering. Please help

I’m growing out doors in Southern California and I’m around the 4th week of flower I’m using a 7 gal pot an fox farm soil and fox farm nutrients as well I’m watering the plant at a ph of 6.3 or 6.4. I’ve been seeing lots of yellow leaves dying of an at fist it seemed to have started at the lower part of the plant an now it’s making it way up an affecting higher parts . Can it be a cal mag deficiency??? What do you guys think ?

Watch and wait. It’s normal.