I ran into this a lot when I ran Coast of Maine Stonington in pots, I have always felt it was a magnesium deficiency caused by out of range ph. Check soil ph, apply epsom salts or cal mag. Eventually those yellowed margins will go brown and the affected leaves don’t recover it’s a game of stopping the deficiency while it’s showing up on the lower older leaves. Honestly never fully worked the issue out just moved to giant beds of soil and that supply’s enough buffer for a stoner like me