Is the "spam update" reason that my sites are not getting indexed?

In past 3 days none of my website are getting indexed on google (Discovered - currently not indexed) whereas earlier they used to get indexed in about 5-7 hrs. What should I do to solve this. Also I have a lot of sites (60%) under "URL Need Improvement" category in Core Web Vitals, is it the reason my new sites are not getting indexed?