Finally, someone with some good advice. To add to Bill's comments, the typical wall plate can feed two TVs. One TV can go to the front connector and another can connect to the back side of the wall plate. Most likely the feed on the back side is going to a splitter that feeds the other two TVs. As stated, make sure all connections are tight and that the connectors are installed properly. Also, make sure that the coax cables are in good condition. No cracks or cuts.
Here's a link to a good article by Chris Bryant:
https://web.archive.org/web/20130814121735/http://blog.rv.net/2008/06/tech-tune-up-your-tv-antenna