Difference in hash rate for identical Rx580s

My rig has 9 Asus Rx580 8gb without any bios modifications. Five of the GPUs work with 26-27mh/s rate each so it is pretty well for a stock rx580, whereas others four GPUs have only ~22mh/s each. GPUs use the same driver (amdgpu-pro 17.50), PSU, OS (Ubuntu), ...

rocm-smi tool says:

GPU Temp AvgPwr SCLK MCLK Fan Perf SCLK OD

5 69.0c 143.27W 1360Mhz 2000Mhz 53.73% auto 0%

3 61.0c 133.48W 1360Mhz 2000Mhz 42.75% auto 0%

1 69.0c 135.240W 1360Mhz 2000Mhz 74.9% auto 0%

8 69.0c 146.145W 1360Mhz 2000Mhz 49.8% auto 0%

6 69.0c 129.114W 1275Mhz 2000Mhz 60.0% manual 0%

4 73.0c 118.127W 1275Mhz 2000Mhz 76.86% manual 0%

2 69.0c 147.229W 1360Mhz 2000Mhz 73.73% auto 0%

0 72.0c 140.133W 1360Mhz 2000Mhz 85.88% auto 0%

7 69.0c 134.40W 1360Mhz 2000Mhz 42.75% auto 0%

2, 3, 4, 7 - work with ~22mh/s 0, 1, 5, 6, 8 - give 26-27mh/s

I had to decrease sclk for 4, 6 because of overheat they too close to each other.

Is it ok?

I don't know how to find GPU memory vendor on linux. So 2,3,4,7 may by Hynix 0,1,5,6,8 - Samsung. How can I check it without Windows?