Thank you, guys. I learned from the vet that he had a tumor in his abdomen, and it likely tore away or otherwise caused some bleeding. He was 15, and wanted to play a lot longer than usual yesterday. It was probably a ticking time bomb for something like this since he was a religious fanatic about that yellow orb of goodness, and the alternative was getting sick over the coming months. He definitely had a better time playing ball to the end, and I'm very grateful he didn't have to deteriorate in illness.
Our hearts are broken, but especially my step dad's. He's worried that Ashi will be lonely, even though my lgds are there most of the time, and Theo and I walk up at least once a day. I think it's the other way around, and he enjoys the ball game as much as the dogs. (one property, two houses, same giant yard - no one is ever lonely around here!)
Thanks again.