ya i agree my 1 month old cort mr730fx was send for a setup due to high humidity in singapore back in august =(. i suggest you go back to the shop and ask them to adjust the truss rod for you
If the humidity is causing the change, then you'd be sending your guitar pretty often for a setup. Why not just save the trip and cash and adjust the truss rod yourself?
You'd learn how to adjust a truss rod and you'd know how it works, gain more knowledge. It good to know the insides of your guitar
for all you know that fret might just pop out a little. the possibilities are endless though. have to see it before we can conclude anything. however, its best to send it back. see if you are lucky enough for them to do it for free.
it's good to know how to adjust truss rod BUT must take extra care while doing yourself. It's best not to turn more than one turn of the truss rod either way.