Airport Extreme 6: Slow download, fast upload

Apple Airport Extreme 6 has slow download speed but fast upload.

Have fiber optic service with 400 mps download and upload speeds. 3 extreme 6 routers all hard wired together. Two of them are speed testing at the 400mps upload and download. One is only 100mps download and 400mps upload. I swapped out the locations of all three and the slower one is always giving the same speeds and the faster ones are working fine at all three locations. I tried resetting a couple times and firmware is up to date.