I have created full text search in webforms using Search Api and its working fine earlier but when i added some new records, the new records are not indexed and not able to displayed them on view. I don't know why new records are not indexed.
You'll need to re-index the site when new records are being added. You can do it by visiting http://your-site-url/admin/config/search/settings and click "Re-index site".
P.S: This will queue the items for re-indexing. The items will actually be re-indexed when "cron" runs for the next time (manually or scheduled cron job.