The DL has been good/great all year, they didn't hit the wall and look gassed until after the KC & Buffalo games. 172 snaps those two games is the most by any defense in a two week stretch this season. It's no coincidence they came out hot in the 1st quarter against the SF OL (which is average at best in pass protection) and then as that game got into the 2nd quarter their legs were gone.
Sweat & Reddikk have piled up a ton of snaps, Carter & Davis have never reached the 400+ snaps territory they're in now, etc - just another reason why getting that bye and week of rest is pivotal for that unit to be able to dominate. Just find a way to win this Seattle game by any means and the goal is within reach.