4K Footage playback lag on PC I built for 4K editing

I followed some online build guides with the intent of editing 4K videos. Earlier this week I just bought two new SSDs and put them into my system thinking this would solve the problem. I've got my OS and software coming off one SSD and I've got my footage coming off another. Then I've got my scratch disks and cache coming off a non SSD drive. And I still have lag, makes me want to pull my hair out.

Here is my build.

Processor: Intel i7-6700k CPU 4.00 GHz 4001 Mhz 4 Cores

32 GB RAM

GeForce GTX 1070

SSDs: Samsung  850 EVO 250 GB (OS and Software)

Samsung SSD 850 PRO (Footage)

And then Ive got two non SSD drives

Im running Windows 10 and the newest version of Premiere Pro

Does anyone have any thoughts?

[Moderator note: moved to appropriate forum]