Low hashrate with some algos using riser

Hi, I bought some days ago some gpu and riser to make my first mining rig.
I recived only the riser today so I tried if they are working well with my gaming gtx1060 6gb.
I made some benchmark algos using the lastest ccminer with the gpu installed directly on motherboard.
When I installed the riser I saw that some algos lose hashrate. I'd like to mine nist5 when the new will arrived.
For example with the motherboard connection I got about 31 MH/s using Nist5.
When I mount the riser I got only 20 MH/s.
I tried dagger-hashimoto algo and neoscyprt too and I didn't lose hashing power.
For now I'm using an old Z87 motherboard and I'm waiting for a new Z170.
The monitor was on CPU graphics output
Is it normal that 35% lost just on some algos?

Thank you guys!
P.S. Sorry for my English.