Wordpress Multisite Domain Mapping with SSL not working

Hi. I'm trying to setup my multisite network so that both onlinemenuplatform.com and munchthru.com are forced to be delivered over HTTPS. Currently, munchthru.com appears to be working (although https isn't being forced and it should be) which is great as this is a live e-commerce site and is the main priority on the network at the moment, but onlinemenuplatform.com is using munchthru.com's SSL certificate and I don't know why. They each need to use their respective SSL's which are installed on the server. I'm almost certain it's to do with my wp-config file being setup incorrectly but I'm struggling to see what's wrong. Thanks!