Doesn't seem to be pihole calls. Pihole was running on a Raspberrypi connected to the main router. I am thinking a malware somehow got on the RPi is calling anything on the network with a port 80 with the calls I mentioned above.
I haven't used PiHole but it looks like a practical use for one of my PIs currently collecting dust. Other than this issue how have You found it? Does it do a good job of blocking adds?
74.64.250.142 is listed on S.O.R.B.S, my tablet battery is dying so can't check them all.
But You might want to search the other IPs on