If it's a chap in need of some mozzy spray I think we've been looking at the same youtube clip
If one cylinder was very low - as his was - I'd be repeating the test after putting some oil into the cylinder. If the reading then went up I'd suspect rings/bore/piston damage.
I've also been looking for a service manual for yours online, lots of owners manual that just give compression ratio free to download but the service manuals generally are on pay-to-download sites - - although I've just checked the service manual for mine & it makes no mention of compression test results.
If your plugs were older a steam cleaned look is a giveaway that a cylinder has had water into it.
Difficult to know which way to go, but in the absence of any other suggestions - or the problem having gone away after what you've done so far - I think the next step could be to remove the head & examine the bores & the state of the gaskets.