We have a SharePoint Foundation 2013 server (SQL separate) and we applied the last March 2016 CU Update to it. But the user that applied it did not run the PSConfig tool immediately. I ran the PSConfig afterwards (like 12hours after the install). The server wasn't updated since a while. We reinstalled it last year with Service Pack 1 (15.0.4569.1506).
We have a rather large list (45099 items) and we now have the problem that the dispforms and some other pages are having a slow page load (6 - 11 seconds). Everything seems to be running fine. CPU, Memory,... are the same like before the update. We checked the Distributed Cache and everything is healthy. We disabled search and checked if that did something to the performance, but it didn't change anything, so we re-enabled it.
I hope someone can give me a hint on where to look further.