The info is sparse at best it seems. The Tx SOS website shows that only
Cornyn and Mapp have filed as of today. Yet Wyatt says he has based upon
the link you have. So who knows at this time. I find nothing on Vega yet.
https://webservices.sos.state.tx.us/candidate-filing/cf-report.aspx
You have to select Travis County from the list as Austin is where they have
to file for the primary.
The Texas GOP website with filings says that Stovall has filed also:
http://www.texasgop.org/elections/candidates/#United%20States%20Senator
Thanks and take care
We probably have to call the SOS for updated filings.