We have two full baths on our second floor. In our guest bathroom we have a tub/shower. After bathtime and we drain the tub there is a reddish grit left on the bottom of the tub. This doesn't happen anywhere in any of the sinks or the master bath shower. Does anyone know what this could be and/or what I should do to try and find out what it is? I have already spoken with my plumber and he was miffed.