Tracing non-uniform slowdown on a multisite install with multiple domains
I’ve got a multisite install. By default, new sites are on subdomains. The host is not the fastest, but given the price, not too bad.
Recently, I updated the install to use extra domains. The domains are parked as add ons to the main install. I changed the base link and domain for the sites I wanted to use new domains with and added a quick redirect to the .htaccess so I don’t have to worry about old links. The time to the first byte is 10 to 20 seconds but only for the new domains.
I’ve checked with customer support and the domains are definitely resolving at the same speed as the main domain. It is not plugin related because even sub-sites using few if any plugins are the same and the problem is not there for subdomain subsites.
Is there a known reason why the lag happens?
Assuming not, what steps can I take to try and reduce this lag?
Specifically, are there any areas I should investigate to try and find a solution?