It’s not “best practice”, but a compromised key is a compromised key whether that key is used to connect 1 or 100 computers to a server. No, I can’t shut off access to exactly one machine, I do not however have any difficulty in shutting off access to every machine and replacing it with a new key. Your system and my system are no different with a single compromised key.
If I had 100 computers that I had to change identity files on each time it was compromised, and my keys were being compromised often, I would see a benefit from using multiple different keys.
Quit acting like I’ve left the front door to my house open when the door is locked but my roommate and I share the same key.
Glad to hear it worked! I edited the comment in case anybody stumbles across it with the same issue