Can anyone help, 

The last few fondant cakes have really bulged.  Each cake was wrapped in clingfilm and weighted down. Then filled and weighted again for a few hours. 

Then coated in buttercream once set I covered in the right amount of fondant and left to dry before stacking. 

I set the cake up at the venue and all was well, but looking at the wedding cake cutting pictures it's bulged. The room was humid and it was raining but apart from that I don't know what else to do to stop this from happening. 

Any suggestions would be much appreciated. Thanks xx

I was taught that the b'cream crumbcoat had to be fresh, wet so the fondant had something to stick to -- eliminating the posibility of buldging.   Weather like that is not our friend.  It can and does cause many problems.  I'm rather sure it was a combination of the poor weather and not anchoring the fondant well enough

I didn't know the tip from kakeladi about applying the fondant before the buttercream set - thanks!  I agree the weather was probably mostly at fault.