Amy Bowers

To be honest, I wouldn't know how to do that. Not sure where I would find the old legacy world nor how to backup our current world. We have done the vast majority of the work in the game after we converted.

My newly spawned horses won't enter love mode but I can see their health. 

It is a converted world and it has been quite awhile since we converted. Does this problem impact horses that have been recently tamed or just all of them?

Yes, they both have been tamed.