Period/full stop replaced with comma in numeric keyboard

Hi all, for a few of my apps that require the numeric keyboard (tax app, banking, etc) the full stop/period has been replaced with a comma. This makes it impossible to put in any cents and pretty much renders the app useless. My calculator is doing the same. And I can't work out how to change this (or if it's even possible). I've checked all my keyboards and region settings - all good. Not sure if this is an app issue or Apple solve. Help appreciated - it's driving me nuts!