The stone of reformation is for Traits, and has no effect on Tradeskills that I've ever heard. And there's no cap of any kind which would cause your XP to hang at level 25.
When reported this usually ends up being a UI corruption and you're really still earning the XP. Are you using a custom UI? If so you might look for a current version of it or just go back to the default.
If you're using the default UI I'd get into your EQ2 UI folder (probably at C:\Program Files\Sony\EverQuest II\UI) and delete everything, then re-run the launch pad and have it do a thorough filecheck (under Options on the Launchpad). This will reset your UI with fresh files.
If that doesn't work delete any file with your character's name that ends in "ini" and do the same procedure.
If you do all that and it's still acting up, /petition to see if there's a problem with your account. I'd link this thread and tell them you've followed these suggestions and you're still not getting XP. If the GM's can't help note the help ticket number and call customer service.