Site traffic halved not sure why

[BrisbaneSEOWorks]

Hi guys, not sure if anyone can help, but we had a client's google organic traffic literally halve from the week at the end of August to September (29 Aug 2016 to be precise) and it hasn't recovered since (here's a screenshot from GA http://puu.sh/sAmd3/b071dd1e57.png)  I've been doing a lot of digging around on Moz and elsewhere about any Google updates that may have gone through around that time and there doesn't seem to be anything that I would think would affect it.  I thought it might be to do with Penguin, but that doesn't seem to be the case.  A while ago before then we did have some domains and pages 301 redirected to the main site when multiple other sites were rolled into the one, but I wouldn't have thought that should affect it.  After that I've also gone and removed all those sites and redirects too (couple of weeks ago) but that doesn't seem to have fixed it.  There's no black hat SEO done on the site so very odd to have this happen.  I'm rather out of ideas what it could be that has impacted things so suddenly and that we couldn't get it recovered from.  Any ideas would be much appreciated.

[Martijn_Scheijbeler]

Hi,

So did you check in Google Search Console if there are any more errors that you noticed or any volume in terms of keywords that has gone up or down? Usually with your amount of weekly traffic it could be a penalty but it's also still very likely that just your traffic on a couple of higher volume keywords went down and that's what you're seeing in your analytics data.

Another thing could be to check what kind of landing pages from organic search were affected so you can get a better sense of what's happening across your site. Because with this decline it seems unlikely to me that potentially all your pages were affected.

Martijn.

[BrisbaneSEOWorks]

Hi Martjin,

Yes, this is the first thing I checked.  In fact I checked it in GA > Acquisition > Search Console which enables you to filter the data quite well by regex.  What I found is that it's pretty much across the board with the homepage as well as individual product pages taking a hit of around 50% reduction.  It's definitely NOT traffic on a few higher volume keywords as the major drop that's hurt quite a lot is traffic to individual product pages.  That indicates to me that it seems to be some kind of a site-wide penalty.  I did also notice that traffic to product print pages (where the product is in a print-friendly format) effectively went from say 300 to like 30 (and probably not much can be done there), but it's the overall traffic from SERPs that's more concerning, particularly to long-tail product pages.  So I'm pretty confident it's some sort of a penalty, but no idea why it's would be applied besides what I've already flagged in my original post