Not gaining experiece?

[Zechs]

I have 86 stamps and level 50 cap, but my characters that are lv 45 aren't gaining experience from boss fights anymore? Any idea why?

[Luma]

If your characters are 5 levels above an enemy they won't gain any experience, that's why your lv 45 characters won't gain exp against lv 40 bosses.

Here is a really great guide for farming exp : https://steamcommunity.com/sharedfiles/filedetails/?id=3443486599

[Vinnolo]

save your xp data for the last 5 levels, which are by far the hardest to level up, since all you can do is beat high level fractal enemies and farm chests to get xp

[Bishop]

After 45 you just have to farm red series in fractal. It's kinda boring, but you have to run through it anyway to get better gear, so may as well combine these things.