If you OS changes aren’t doing the trick for these apps, here is a found nugget.
You have to do this with the (typically) Advanced Config Editor. Search there for layout.css.devPixelsPerPx. When you find it:
change its value to 1.0 and click OK to save it. This will give you classic 96 dpi fonts. To enlarge that by 10%, double-click and use 1.1 and click OK. And so on. You may want to switch around between windows and tabs to see how it’s affecting them.