apache – Different SSL certs being delivered to different platforms

I received reports of an invalid SSL cert on a site that I recently started managing. Testing it on a Linux PC and a Windows PC, I find that the cert being delivered is different from the one delivered on an Apple mobile device.

The server is running Apache 2.4, and I can see that the invalid cert is set up in /etc/httpd/conf.d/ssl.conf. The correct cert is set up in /etc/httpd/vhosts/mydomain.conf.

Is this a common issue? What’s going on here? (I don’t want to make big changes to the server config because it’s been around since before I got here, and Apache is serving multiple virtual hosts.)