longjorn on "[Plugin: Yoast SEO] Fetch as Google no Index..Idea of solution"

don't want to start a discussion about www or not, but if you have subdomains 'below' your main domain, eg: sample1.domain dot com and sample2.domain dor com, search engines will mix them up with domain dot com if this is not using http://www.domain dot com
just my experience - might be wrong - I use www