Jeff -
The coho in those areas would likely be a mixture of Snohomish and Stillaguamish and Tulalip hatchery fish as well some headed towards South Sound.

Preseason forecast (prior to any fishing) for the returns the Snoh/Stilli area was for a hatchery run of 49,000 (as I recall only a 1/3 or so were clipped) and a wild run of 230,000. So yes the coho run is healthy (though marine survival are expected to be low average) and it is not surprising that you are see low numbers of clipped fish.

Tight lines
S malma