This is how it looks like - its always fluctuating in between 160 and 180.. Is this normal or shoud I do something here?
Only GPU 3 and 4 that always fluctuated? (as shown in your pics) If it yes, you can focus on those two.
Drop until 8 MH/s on each (GPU 3 and 4) isn't normal, you can start with check memory error (since you are using AMD card you can use HWinfo)
Sometimes its all of them. For example, my hashrate is at 180 MH/s and suddenly it drops for a few seconds to 130 MH/s, but then goes back up again..
So what should I do exactly with memory error?