If they have green arrows, it means they are doing well. They might have improved attributes, but it'll be fractional and not enough to change to the next integer yet. You can click on the attribute name and it'll take you to the training screen where you can see if it's improving, even fractionally.I'm not sure if it's a bug or not.
Players are developing and have green arrows next to their attributes, but the numbers aren't changed.
Is it happening to anyone?