Text box doesn't line up after changing paper size for novel

Hi everyone, 

I've been designing my novel with the dimensions 5.5 x 8.25 inches, but I've decided midway through the project to change to a 5.5 x 8.5 dimension (mostly because KDP doesn't offer the former). This has caused a bit of an issue though, in that my text boxes now don't line up to the new dimensions. I'm not sure what to do, and I really don't want to have to start over with my design! Is there any way to get the text boxes to resize to the new paper size? 

I've attached an image of the issue down below. I'd appreciate any thoughts on how to fix this. If worse comes to worse I'll just start again, but I hope I can avoid that!