I'm worried that your toilets only appear to drain slowly because of the type of toilets they are. Has their performance changed or have they always been like this?
If you are new to the house and just the bath and sink drains were draining slowly then I would suggest that this is just normal buildup (hair).
My sink and bath drains always slow over time and need to be cleaned about once a year or so (my wife has long hair). I use chemical cleaners for these (a whole bottle in each left over night) which most of the pros on here shy away from, but with a slow (rather than a blocked drain, which needs professional help) they work just fine for me.