Dual Dell Monitors Causing Different Problems (P2415Q and U2715H connected to HP Desktop with AMD Radeon 7700)

Hi. Multiple issues here:

1. I have a Dell P2415Q that works perfectly when connected to the display port (single monitor).

2. However, when I connect my 2nd monitor (Dell U2715H) via the HDMI port, the computer ceases to recognize the P2415Q and it thus turns off and everything moves to the U2715H.

Ideally, I will be able to connect the P2415Q via the DP and the U2715H via the HDMI and have it all work fine. BTW -- it was working fine that way for a few days, until it suddenly stopped for no apparent reason!


PROBLEM 2:

If I switch the cables and connect the U2715H on the display port, then it works fine. However, the p2415q connected to the HDMI port works very "slowly." The best way I can explain it is to say that, it does not run smoothly compared to the U2715H. Things "drag." Screens flicker. Skype video all of the sudden is glitch-ridden and does not really work. Video will play but not well, and overall it's painful to use because of how slow the monitor is working.


I have tried downloading new drivers via the control panel; downloading the AMD Radeon auto-detect program and letting that works its magic.

Note that I have an HP desktop with an AMD Radeon 7700 graphics card. And that I usually downscale the P2515Q to match the pixels on the larger screen (so from 4k to 2560x1440).

PLEASE HELP!!!?? THANK YOU!!