Do blank passport pages have to be consecutive?

A page is blank if it has nothing on it. Stamps on subsequent pages are irrelevant, a blank page is a blank page.

Some countries may have rules about needing (for example) two consecutive, facing, blank pages (so a full-page visa can go on one page and the entry/exit stamp on the one facing it), which could rule out the use of some blank pages for those countries.

I’ve never heard of a country requiring blank pages to be after all other stamps. If there is one, I’m sure their rules would make that requirement explicitly clear.