Like Mary, I'm not a guru, but don't think it'll harm your SEO, but:

• What does Google display for these sites? If the
  is displaying in search results, that's 4 of your precious characters wasted that could be used to convince people to click on your site.
• What do browsers do when they encounter a
  in a title tag? It might get kind of ugly up in the tab or title bar.

TL;DR: If you can get rid of them I would.

That's not so horrible - it just says not to crawl the plugins directory or the admin, and to delay a second between requests. You probably don't want your plugins or admin directories being indexed, and according to this old forum post Google ignores the crawl-delay directive, so the robots.txt isn't the problem.

I don't know why this is happening, but this is what I would check:

• Do you see any crawl errors in the Google Search Console?
• If you search for your site on Google, what do you see, (does your snippet look normal)?
• How many pages does Google say it has indexed? Is it possible it's indexed everything and is taking a break, (does it even do that?)

One theory is: When you moved to the non-www version of the site, Google started getting 301s redirecting it from www to non-www, and now that you've gone back to www it's getting 301s redirecting it from from non-www to www, so it's got a circular redirect.

Here's what I would do to try to kick-start indexing, if you haven't already:

• Make sure you have the "Preferred Domain" set to the www version of your site in both the www and non-www versions of your site in Google Search Console.
• In the Search Console for the www-version of your site, re-submit your sitemap.
• In the Search Console for the www-version of your site, do a Fetch as Google on your homepage, and maybe a couple of other pages, and when the Fetch is done use the option to submit those pages for indexing, (there's a monthly limit on how much of this you can do).

Good luck!

I'm not convinced that robots.txt is causing your problem, but it can't hurt to change it back. In fact, while looking for instructions on how to change it I came across this blog post by Joost de Valk, (aka Yoast), that pretty much says you should remove everything that's currently in your robots.txt - and his arguments are right for everything:

• Blocking wp-content/plugins will stop Google from loading JS and/or CSS resources that it might need to render the page properly.
• Blocking wp-admin is redundant, because the wp-admin if it's linked it can still be found, and important pages already have an X-Robots HTTP header that says not to index them.

If you're using Yoast SEO, here are instructions on how to change the robots.txt file.

I thought of one other possibility: Your sitemap.xml is probably auto-generated, so this shouldn't be a problem, but check to make sure that the URLs in the sitemap.xml have the www.

Other than that I'm out of ideas - I would wait a few days to see what happens, but maybe someone else with more experience watching Google will have seen this before. If it does resolve, I'd like to know what worked.

I'm implementing Schema.org, (JSON-LD), on an eCommerce site. Each product has a few different variations, and these variations can change the price, (think T-shirts, but blue & white cost $5, red is $5.50, and yellow is $6).

In my Schema.org markup, (using JSON-LD), in each Product's Offer, I could either have a single Offer with a price range, (minPricd: $5, maxPrice $6), or I could add a separate Offer for each variation, each with its own, correct, price set.

Is one of these better than the other? Why? I've been looking at the WooCommerce code and they seem to do the single offer with a price range, but that could be because it's more flexible for a system that's used by millions of people.