we are working with some custom control templates and deployed web parts, there is content not appearing recently we added in web parts and site pages design, here how to track deleted content and deleted site pages. There is no change happen at the content database level.
There are two options:
1) Recycle bin (documentation) - look from UI or write PowerShell script, that logs all new content in recycle bin. As admin, You can see all content that users have deleted. Recycle bin will only store list or library data - list items, documents, document sets, pages etc, but it won't store webparts, design changes and other layout-related stuff
2) Since You have custom solutions, You can add Event Reciever (good explanation by Chaitanya Singh) and log information about all content that is deleted in local file, custom database, service or how more convenient for You.