Is the traffic the same as it was before? Please answer this.
Which hosting you are using? GTmetrix is not as reliable as Pingdom when it comes to page speed. Your site when loaded from a US location is loading in 1 second, but from australia it is loading in 3 seconds or more. Just asking, can you afford a CDN like MAXCDN? Or can you try its trial version for 30 days. Because urs is an image heavy site.
Total indexed pages are increasing because of AMP. And this drop in traffic might be due to many AMP errors possible in WP for AMP plugin which u are using. Thoroughly search the AMP section of your google search console. You will find that google is already showing errors for AMP. Now resolve those errors one by one. What happens is, google might show AMP pages instead of mobile pages for your site. And then when there were serious AMP errors, it might stop showing AMP pages at all. Ultimately, your site loses traffic and rankings.
And your AMP version has 4 ads on page! Whereas AMP is not supposed to have ads. One of those ads is a 300 x 250 ad which is generally frowned upon above the fold. So push it down a couple of paragraphs if possible.