Blog post indexing

I have relatively new site 4 months, low competition niche.
Site has claimed the ranking nicely.

BUT i have blog posts that are NOT indexed. I posted 3 blog posts around the same time.It has been months already. One of them indexed, other 2 did not index, all are quite good quality. Any ideas why is this happening?

Have you checked all pages on google page insights?

Are they similar articles/topics?

pls check robots of page

How many words are they and how many images each of them contain?