Hi, I've installed two outdoor receptacles (outdoor housings, GFCI outlets) off of a 110 line (GFCI outlet) in my shed. Every so often, the GFCI in the shed "trips" and kills power to the two outdoor outlets. It usually happens after it rains...or has been damp. How should I go about troubleshooting this? Is there a methodical way of going about this rather than just working my way out from the source? Thanks for any help.