Can anyone advise please? or comment?

I have a batch 2 Z9 Mini overclocked to 650, so not pushing to much, getting all three cards hashing and an average 14.5. No HW Errors....

However, i get approx 30 rejected shares in say, a 24 hour period?

Is this good/bad? Is this to be expected if overclocking? Should i reduce overclock?

Thanks Guys