Maple's results came back, and her white count is back down to normal. FIV test (which our vet likes to repeat 90 days after a cat leaves a rescue/foster situation) was also negative. All good! Not sure all Byron's numbers are back yet.
After even one dose of the anti inflammatory Rx, Josie felt SO much better. She's got another week of meds and is still on exercise restriction, so it's 1 block walks for now, half a block to the stop sign and back. I'm glad we didn't stick with the "wait and see" approach. Also, I didn't realize until the vet did his exam and was talking with me that his biggest concern (given her age) was cancer, very relieved there was no sign of thickening in bones or lymph nodes, and her response to the Rx also backs up the theory that the problem was "just" overdoing it at the beach.
for both Ronnie & Ginger... and for anybody else who needs one!