Check if you've been "helpfully" set to "top tweets" vs. all tweets, in the settings. Algorithms are great!
The default text size also got smaller and changes to text size and colour customisation aren't getting persisted, so I assume something's busted.
[1] https://github.com/insin/tweak-new-twitter#tweak-new-twitter
I follow over 2k accounts, so the odds of the most recent tweet being 45+ minutes old is low.
I also double-checked some of the people I am following, and indeed their most recent tweets are not showing up in my home timeline.
This is happening across all my devices (mobile & PC), so I assume it must be an issue with their infra that is limited to a subset of their users. Possible an issue with a cluster?