Port Scans From Within Home Network

The problem started on July 12, 3:45pm, when computer A was port scanned by computer B (both on my home network, BOTH with Total Security 2015). Five minutes later, computer B was scanned by phone A (a Galaxy S4) AND computer C was scanned by phone A. Since then, four of the five computers (two wired, two wireless) on my home network (all protected by Bitdefender) have been sporadically port scanned by phone B--also a Galaxy S4, and one of the computers was port scanned once by our router. But not close to the same time, and sometimes not even on the same day. My router, sadly, does not keep a firewall log, and I can never catch whatever is going on with wireshark.

During my search for answers, I stumbled upon a Bitdefender forum post from 2011 (http://forum.bitdefender.com/index.php?showtopic=28686) where someone had a similar problem, except we changed nothing when these scans started occurring. But I figured maybe someone else has had a similar problem, or at least an explanation as to what *might* be going on. The holder of phone B, which has been the only device causing the port scans since the 12th (with the exception of the router port scan), says that she is reblogging on the official Tumblr app or cropping pictures using the phone's default image viewer. But she does this throughout the day, and the port scans the four computers are picking up don't appear to match that schedule (as entire days go by without incident).

Any ideas as to what's going on?