RTX 2080 Underpeforming

Feb 2, 2019
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Hi, I just upgraded to a 2080 and have gotten massive performance issues. I can barely push 150 fps in fortnite at all low settings, I can only play forza horizon 4 on all ultra settings at about 80fps (not sure if that's normal or not but I feel like I should get higher.)
I've singled it down to my cpu, but even then I'm not sure.

System Specs:
ASUS PRIME Z270-AR
2x8gb Ballistix Sport Ram @2400 mhz
MSI RTX 2080 GAMING X TRIO
Intel i5-7600k
 
Feb 2, 2019
11
0
10


Is there anything I can do to pick up the performance? I don't have enough money to upgrade my cpu right now as I didn't count on this happening.