Stop multisite from directing subdomains to https

I have SSL setup for the primary domain of my multisite installation and I am using subdomains for all the other sites under it. The problem I am running into is during signup and other times, when WordPress directs/redirects to a subdomain site, it always uses https, when it needs to used http. I only have a certificate for the main site, I don't have a wildcard certificate for the subdomains.

I tried changing my nginx config to redirect https to http, but it cannot be done without a wildcard certificate for the subdomains, which is the problem I am trying to solve. Therefore, it brings me to WordPress to solve the problem. I need WordPress multisite to always direct to http for all subdomains. It is even alright for it to direct to http for all domains, since that is easy to redirect in nginx to https when desired.

Any suggestions?