Grey water(baths) and Black water (toilets) drainage issues all at the same time indicate Main sewer
partial blockage from tree roots, washer lint buildup, feminine hygiene products, kitchen grease and excess disposal sludge etc.. Should be a tapout in the sewer to open or the plumber will put one in when he snakes it all out. As long as pure
Stygian Black stuff

(blow
all ballast!) ain't backing into the tub, you're not in
reeeeeal tuff shape...yet! It's still going, albeit slowly,
in the right direction. Could also be a frozen/split bath drain in the wall from the tub depending on your recent Polar vortex temperature issues if leaking in the house wall/ flooring, though, as you indicated.. Have had
all of the above myself...had to cut down the tree and replace the original 40 yr.
Asbestos 30' sewage line too

trench warfare if ever mingled with joy of home ownership!