We were following closely this update and we actually "managed" to recover a site that lost about 50% of its traffic and revenue, 100+keywords lost more than 50+ positions from SERP, and now everything went back to normal around 2 weeks ago and even better.
I will suggest the steps we took to recover from this but note that there were 3 stages of recovery! Meaning since 1 of august we saw 3 stages of websites recovering from the update, at this point we cant tell if the recovery was from our fixes or naturally from the algorithm update.
But we know why sites went down, Google evaluated how trust worthy articles and products were for the buyer and the information provided about them.
This is what i suggest:
Who is authentication your products? Link the clinics or doctors who authenticate your products their medical background and most information you have about them, create a page for doctors.
Correct the product cattegorisation, you mentioned a incorrect
categorisation which was affected as well from this update try to
keep your products in this order:
General health > Stop smoking > Product
Category > sub-category > product/article
If you have a Blog internally link articles to the products to
create information relevancy.
Amend content given for products, this update affected sites with thin information about the products,b should be enough information since is a medic topic.
Amend keyword placement taking into consideration users intend. Here
is a quick best practice on where to include your keywords on the
- Beginning of the title
- Meta Description
- As early in the content as possible
- 2-3 keyword variations in text/content
- H1 The exact keyword
- H2 Keyword variation
- On your URLs
This is a YMYL site and Google took into consideration users health, i know you mentioned your site doesn't sell to costumers but it still falls under the YMYL category.
Overall try to show Google the background of your products and that you give enough information.
There are a lot of articles out there about this issue if you haven't recover since the algorithm update i would suggest start making changes and creating some good informational content.