I am having issues with indexing some of my pages at my 1 year website.

The site is going pretty well. The clicks and impressions are increasings.

But i have indexed only 150 pages from 200 published. I have done many internal links to these 50 not-indexed pages, external also. I am confused what is the reason. The site is not so fresh already. More than 12 months I am doing everyday updates and visits are increasing.

Is there anything special I can do to index these pages?

Thanks