Sunday he vomited and though he ate with a little coaxing, he wasn't enthusiastic about eating. In the evening he was acting really mopey. He didn't want to get up to go outside with the others and he just wanted to curl up and stay put. Monday morning I looked at his gums and they were almost white. That sent us to the vet clinic immediately.
He's now eating prescription I/D food coated with pig pancreas powder and taking an antibiotic. We're cutting out as much fat from his diet as possible. Yesterday he was obviously not feeling well, but today he's feeling much better. he was even up for a walk around the park this morning.