Help! I would appreciate your opinion

I would appreciate your opinion

I had a blog that appeared in position 44 of Google for a keyword and a few days ago I made two changes:
1 - I changed the template for an older one that I have been using on other blogs.
2 – I insert a plugin "wordpress-seo-Yoast"

The blog simply disappeared from the google search with the keyword (but still appears by the url)

Yesterday I inserted a new blog (with the template and plugin referenced above) in a subdomain of a blog that was in position 6 (pag 1) of Google and he has vanished from searches.

I think it must be because the plugin because I do not see the template to do this effect, but I'm not sure.

Someone can give an opinion or has experienced something similar?

Peter

Yes, changing a theme WILL impact your wordpress ranking. How do I know this? I own a very popular WP site. Everytime we release a new theme, rankings go crazy, but they do come back.

I am using Wordpress SEO by Yoast on my 2 wordpress blogs and i have no issue with it. Changing your template may affect your ranking but Wordpress SEP plugin? I dont think so. For me, Wordpress SEO is the best plugin from any other SEO plugin.