I have a few theories – but that’s all they are, theories. Google changes their algorithms all the time, trying to offer ever more relevant and quality search results to users.
I would talk to your SEO company about reducing some of the keyword overload you have going on. Google frowns on “keyword stuffing” and you may be leaning in that direction. Definitely get rid of all the blocks of hidden text you have throughout your homepage below each post (I didn’t look at other pages, it may be there too.) For example:
<!--
<div class="signature">
<p>Written by admin <span class="edit"></span></p>
<p>April 11th, 2011 at 12:25 pm</p>
</div>
<div class="tags">
<p>Posted in <a href="https://www.vipelectroniccigarette.co.uk/blog/category/electronic-cigaretttes/" title="View all posts in Electronic Cigarettes" rel="category tag">Electronic Cigarettes</a></p>
<p>Tagged with <a href="https://www.vipelectroniccigarette.co.uk/blog/tag/e-cigarette-filters/" rel="tag">e-cigarette filters</a>, <a href="https://www.vipelectroniccigarette.co.uk/blog/tag/electronic-cigarette/" rel="tag">electronic cigarette</a>, <a href="https://www.vipelectroniccigarette.co.uk/blog/tag/electronic-cigarettes/" rel="tag">electronic cigarettes</a>, <a href="https://www.vipelectroniccigarette.co.uk/blog/tag/free-cartomizers/" rel="tag">free cartomizers</a>, <a href="https://www.vipelectroniccigarette.co.uk/blog/tag/vip-electronic-cigarette/" rel="tag">vip electronic cigarette</a></p></div> -->
Although you could have been doing that in good faith to simply remove your post tags, it could certainly be seen by Google as keyword stuffing/spamming. You should edit your theme files to fully remove the tag section, instead of commenting out as has been done.
You’ve also used the phrase “electronic cigarette” on your homepage over 60 times. (I stopped counting after that.) That’s definitely veering into the realm of keyword overboard.
I don’t know if there’s one simple answer to your dilemma, but you may definitely want to revisit the optimization of your site – and ideally with a firm that understands the particular needs of SEO and blogs. Best of luck.