Dude. You have dropped in rankings but the posts are there on google. Its not that the posts are deindexed.
1) As per the comparison i showed, even if your total google index has dropped, thats good for you. Google is still indexing 250 pages on your site whereas your site has 140 -150 pages only. So the drop from the index is probably not your good pages. It is other pages like archive etc. I think your page 1, page 2, page 3 is being indexed which should not be indexed. That alone is 14 pages of low value content.
2) I checked your links. Some of them are appearing on the third page of google. Possibly you lost a couple of good backlinks to those articles. What happens is, we dont actively track backlinks. But if we do, we will notice the rise of an article which has received a good backlink, and the day the backlink disappears, next day the article starts falling in the SERPS and goes behind some spots. So its possible this has happened for these 4-5 posts which would have received some good backlinks but the backlinks are gone now. You should take free membership of AHREFS. AHREFS will tell you weekly gained and lost backlinks.
3) I checked your robots.txt and i still dont agree that index.htm should be in robots. I dont know why you have put it there. If there is any reason let me know.
But other then that, the traffic drop is due to proper SEO errors, and i dont think there are manual errors. The only answer to SEO problems is off course, to differentiate your content and try to improve backlinks.
Edit: the reply for was @Rishabh_Sharma1 . I mistakenly replied to @Derek