HTML Content Warning

I recently changed my website in a number of ways.
I added some new products to my main menu.
I also added a few new pages.
I also added some new products to my site.
I made a few changes to my meta tags/titles.

The problem is now I have some googlebot crawl issues. I have made so many changes that im unsure which have effected the crawl!
I now have this message on my diagnostic page (webmaster)

"When Googlebot crawled your site, it found some issues with your content. These issues won't prevent your site from appearing in Google search results, but addressing them may help your site's user experience and performance."

Here are some further details on the changes I have made.
Can anyone help with advice on this problem. I checked my analyitics and my organic traffic has dropped by 75% since the recrawl. Two days ago.

I added some new products to my main menu.
I have added the items to my main nav menu but have not added products yet. So 6 sub menus have the same content on page for example " No products are currently available in this category."
This will be addressed in the coming days so each page will be populated with unique content.

I also added a few new pages.
I have added a links page and few other static pages.

I also added some new products to my site.
I added some products from a new supplier. The details were taken from the information he sent. I have since checked his website and see duplicate content with mine.

I made a few changes to my meta tags/titles.
I changed a couple of tags to inprove seo !!!

Your veiws would be gratefully received.

The warning message that you saw most often is connected with Google's expectation that all your pages will have unique page titles and meta descriptions. If you have duplicate titles and descriptions, Google is likely to think of those pages as duplicate content. If you have recently moved some pages to new URLs without properly redirecting them, Google is likely to have detected the new pages but not yet lost sight of the old ones, assuming they are duplicate. When moving a page to a new URL, always use a 301-redirect from the old URL to the new. I hope this helps!