Water is leaking under the basebaords in downstairs bath. Some water on bathroom floor going under baseboard to dining room next door. House built in 1974. I think it happened after taking shower this morning in upstairs bathtub/shower combination. The sink and toilet in downstairs bath is not leaking. I am on a septic tank but had major work done on septic tank last year - everything has been perfect. Could it be a broken pipe or stopped up tub drain.

I am having my daughter turn the shower on - and check and then maybe later just fill the tub up without the shower on - see what leaks. Thanks for help.

Go inside the bathroom and see if you can find any wetness. Follow it to the source. Yes, it could be a leak inside the wall but it also could be a leak caused by leaking shower door or partially open shower curtain during shower.