Should I be concerned that one boob produces significantly less? Do you experience this too?

My left boob has always produced less but here lately it's not giving much at all. This pump session was 30 min long and I got 3 oz for right boob and 1 oz from left. I was playing with my pump settings and was surprised to see 3oz from my right boob. I usually pump less time and barely see 2 oz total.

My baby nurses best she can but doesn't transfer milk very well. I've still been letting her nurse on the left and I pump normally.

Is this normal in your opinion?