If you have HOA, there are rules

my townhouse HOA has rules for noise controll, no noise making after 10pm and before 8am (which including can't do laundry, fixing stuff, or making noise that disturbs people). I think your tenant can let her kids taking bath after 10pm, but if kids making noise in the bath for 30 mins during the forbidden hours should be prohibited. You can talk to your HOA to see if they have such rules, if they do, get a print out and show your tenant and let them control the noise.