problem with site need help

Is this penalty by panda for bad content?? No link building done, on page i think is fine, content is posted on clean history, very strong expired domain. If anyone expirienced similar problem as you can see on images attached below and know how to resolve please explain here or contact me, i am happy to pay for help. So, after the new posts are published they usualy progress nice and show for many new organic keywords then suddenly after few months posts start to lose organic keywords (first big search volume kws are Lost) day by day until it reach 0 organic keywords or is left with few long-tail useless kws 0-20 search volume which never bring any clicks. This happening to random posts on site and so far i cant find connection (there are posts where writers not use keywords in paragraphs except once in title, and posts where i use few time main keyword naturally and variations all green on Yoast SEO) but this happen on both types of posts. I currently buy content from 3 expensive native english writers so i am not sure if i should blame them, i talked to each they not know why is this happening too they swear they write unique content and using multiple sources, unless they cheating me somehow by rewriting which google can notice and they want to lose business and good client well ok then.. My english is not professional and i not want to mess with the posts myself, but i would love to find out what is causing this to not repeat mistakes as this is 2nd time it happen to me same thing. I am tired of guessing.. First in 2017 february/march i thought its fred update, bad links, affiliate links so i abandoned that site, but now again on another domain which i woudnt like to lose.. i appreciate any help and advice.

https://imgur.com/a/v0M77 site
https://imgur.com/a/H3dyZ random post 1 drop
https://imgur.com/a/ocza3 random post 2 drop
https://imgur.com/a/ixYe3 random post ok for now

Mate Ahrefs showing +-10% keywords means practically nothing.

Use some tracker like serplab.co.uk to track where you rank for the top keywords. And no, 10% lost keywords its NOT a penalty. Penalty is dropping 100 positions for example, or to completely disappear from SERP. But losing 57 from over 3k keywords according to Ahrefs (or any 3rd party source) means nothing. Absolutely nothing.

So far i havent lost 100 positions on any kw that i track i think i would recognize such penalty, i do lose -30 -40 on some but they return next day. Also this number on images change because i add new content, but i lost 300+ kws last 7-10 days i think. Some kws might show on search again ahrefs is slow with update but its pretty accurate, the kws it show i lost not show anymore both on serpbook, accuranker.. with all respect i dont think this is absolutely nothing.. why would some posts advance for 3 months then slowly lose all organic keywords visibility..