Running rough at lower revs, seems rich from the plugs, float level queries

[Nebuchernezzer]

I've decided it's probably fuel I can smell,  seems to have a whip about it even at main road speed.
It only ran on three for probably a second or so and I blipped it and it went away.
I changed the plugs tonight (started fine this arvo by the way), and the old ones didn't look too bad.  The right colour (that tan look),  one was a bit gummy around the top but there is a very slight rocker cover leak around number 3 it seems. Had a bit of a fight with a tiny bit of gravel that had wedged itself in next to the plug but I won in the end.
Carb rubbers look excellent.  My compression tester doesn't fit the small diameter plug holes so didn't try that.
It's probably not been balanced in ages so I wanted to do that however over fuelling or leaking fuel into the bore overnight perhaps could be the problem?
Maybe I'll pull the caarbs and clean them up etc.
Oh and I discovered one of my Carb to airborne clamps is missing but I can't see it causing much issue. I'll replace it regardless.
And the plugs below.