Welcome Joe, I see you have a nice BMW stable and while the R18 certainly is at the other end of the spectrum from your RS and S it should add a great option and a bunch of fun riding.
Some more background may help.
She's not under warranty?
How many miles on her, have you had it since new and was the valve check part of routine servicing at the recommended interval or was the hard starting the motivation to verify the state of tune/adjustments were proper?
If the hard start was the reason, was this a sudden change/problem or gradually becoming worse?
It's not uncommon to get some bad petrol that could cause an injector problem, but odd to be so disparate between the two cylinders unless a some serious crap happen to lodge in the one that won't clear and continually impacted the spray pattern. But, the fact that the plug is wet would indicate fuel is at least being delivered so that leaves spark and air to be investigated. Now that you know the valves are in spec I would keep things simple before any deep dives are done. Verify there is no obstruction in the air intake (mouse nest, shop rag, etc.), and install fresh spark plug. Make sure the battery connections are clean and snug and also the ignition and plug wire connections aren't loose by giving them a simple push and pull. I'd also add some good injector cleaner (Techron, SeaFoam, etc.). I'd start her and see how she's running and if all OK I would try to ride enough to put a couple of tanks of gas with added injector cleaner through her and assess from there.
If you have a GS911 tool or similar that you could check for stored codes may be helpful. Also, if the problem persists I would pull the injectors and switch sides to see if the problem follows the injector and if so have it/them tested/cleaned.
Good luck, try to keep it simple and methodical and please let us know what you find.
