Multiboxing - FPS drops on 2nd client

I’m running 2 clients with each client on a separate monitor. The issue I have is that whichever client is on my 2nd monitor is getting <20 FPS whenever the client on my 1st monitor is the active one. This issue does not happen the other way around however. If I make the client on my 2nd monitor the active one, both clients get a solid 60 FPS until I click back into the other client.

I’m using the 64bit client but this issue is happening on the 32bit one as well. I was away from EVE for a few months so I’m not sure when this would have started.

Hopefully I explained that okay. Has anyone experienced this before?

Edit:
Win10
16GB ram
GTX 970
i7-9700k