help me! The hash rate does not rise.

Nice to meet you.
I am mining etherium with 6 x RX 570.
With 5 RX 570, the hash rate rises only 4 Mh / s and one RX 570 has 25 Mh / s.
The RX 570 with a higher hash rate has a DAG creation time of 5000, and the RX 570 does not rise about 16000.
How can I solve this?
Please lend me the power of knowledge and experience.

soft : Claymore Dual
pool : ethermine
CPU : G3930
MB : PRIME Z270-plus
GPU : MSI RX570 4G OC