if its all wet around the drain and not the top,then its the drain leaking id say.
screw the bottom off and you can inspect the drain.there is a washer down there that can be replaced.this is the one that sound like your problem.i had this problem too,and bought a whole drain from someone.
the fuel heater and schrader valve can leak and make the bottom wet sure,but it's kinda obvious if they are leaking.

you can replace the bowl with the aftermarket filter w/built in drain,however you loose your "water in fuel" lite warning.
i didn't want this,so i replaced mine.
some guys simply use a new washer and bolt.this is what mine would have required because the drain broke.i didn't stop and think,that it was left hand threads and i broke it! i had vice grips on it,it was so corroded,that it didn't want to spin either direction.if i took my time,and found it it was left hand threads first,i could have just fixed it.
the one i found was from a cali truck,and was priced right,so im happy.