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It could be anything, not just the apps you downloaded that day. It could be an update to an older app for example.
To determine what it is, you will have to uninstall apps one by one and test after you have uninstalled each. I also recommend that you restart your phone after each uninstall.
If that still does not help, then the only thing I can think of to resolve this is a software repair using Xperia Companion.