Front spark plug problem or more serious?

Morning,

I started the curvy this morning to take her out for a blast and noticed the exhaust was "popping" (backfiring?) a fair amount and she didnt seem that happy idling - I figured maybe it was just because the engine was cold etc and took it easy for the first 20 mins or so before I picked up the pace. All was going really nice then it suddenly rained and as I made my way home, it kept stalling at traffic lights and was really struggling not to stall and pick up when pulling in 1st/2nd (felt like she was struggling to breathe), then she would suddenly spring into life. Limped home. What I'm thinking is, is this a front spark plug problem (as she only started misbehaving when it rained) or is it something like a blocked carb?
I serviced her myself about 1500 miles ago (new air filter, spark plugs, etc..) and would of thought any of this was the problem it would be picked up shortly after she was serviced.

Any help/pointers greatly appreciated - cheers

[Biker Biggles]

Given that it popped a bit until warm,then ran ok until it rained,then ran like a bag of sh1te pionts to wet front plug.Get it out,dry it out,make sure the drain is clear and put it back with some silicone sealant around the top of the plug well.

Fender extender and some silicone grease around the lead/plug.

Wouldn't use sealant

That sorted it - Took the spark plug out and gave it a good clean (it didn't seem wet, just abit dirty), then bit of wd40 and a load of vaseline around the plug cap. Seems to have done the job and she is running nice again.
Cheers for your help - i'm off to buy a fender extender.......