Hello, we recently spent a year remodeling a home built in 99. We didn’t really use any of the plumbing fixtures prior to moving in but after moving in and starting to use some of the plumbing fixtures, we noticed there soap suds coming out of both a downstairs half bath sink and the upstairs bathtub. We thought it was an issue with the Ikea sink design (I know not ideal) or soap choice but with the bathtub in a separate bathroom doing the same thing, there seems to be a bigger issue. Could a vent issue be causing this? Their placement of one above the other would lead me to believe it is the same vent stack. TIA