I use the Plasma config app to set gtk programs to Breeze.
It has, over the last few days started taking not one or two seconds to start up, but a half minute, even to show the starting logo. It may have begun longer ago, I might not have started the program until recently.
I started it on the command line and got these:
(gimp:3447): GLib-GObject-WARNING **: g_object_set_is_valid_property: object class 'GeglConfig' has no property named 'cache-size'
(gimp:3447): LibGimpBase-WARNING **: gimp: gimp_wire_read(): error
On running it from CLI I also got "can't find adwaita theme" and I installed that, no change to start time, nor look of GIMP, and nowhere do I have adwaita set as a theme that I know of.
I have not changed the hardware, it has been running great.