You might want to give Hermes Lysine while he gets through this ordeal with washing and healing. I have a couple of cats with the upper resp. Herpes virus and I know just what you mean about trying to not let them get stressed. My cat Jimmy just got back from the vet and on top of everything else he's now sneezing and I know it is from the stress of being at the vet and all he went through.
If I know that a stressful situation is coming up, I give them Lysine and it helps them fight the virus from flaring up. You probably already give this to your cats but it might be good to give it to him now, before he gets any further stressed. I give 500mg once a day if I'm giving it as prevention and 500mg twice a day if they are already sneezing.

I wonder if Athena might be taking in extra air when she drinks from the faucet as opposed to a bowl of water. That could cause her to cough. You could try an experiment and only allow her to drink from a bowl for a week and see if the coughing diminishes.

I hope both your beautiful cats will be on the mend soon.