Ads being blocked not only in browsers but in apps too.
Actual Behaviour:
Since updating Pi-hole to V4.3.1, I've noticed that ads are showing in apps that were previously blocked.
I know that it's difficult to block ads if served from the same domain but I think in this case, I'm not sure if the ads would be served via a CDN or via the server on which the app pulls its data anyway.
Either way, I've noticed that ads that were previously blocked are now showing in apps.
You haven't provided any specifics on which OS, which apps, etc. The update to Pi-Hole should not have changed this behavior, since the functionality of ad-blocking is the same.
These tools can help you determine the source of ads.