The only thing I see is an inexplicable difference in the text fonts in my blocks. For some blocks, text fonts have a bold, without this being set as a rule. And it's also in the default ips theme, and also in my new theme, created cleanly after upgrade 4.5.1
When I check in my old themes - created in transitional versions - in all blocks the fonts are the same and without issues.
Here is an example - what two vertically adjacent blocks look like in version 4.4.10
and in 4.5.1