collection experience

I recently completed collections on several alts.
I noticed that 2 of them only got 1.920% xp instead of 2% like the others (same collection)

You have fellowship sharing on.

I didn't know that would influence collection exp.
Now for the next question: how do you turn off xp-sharing for characters that are not in a fellowship.

Then if you aren't in a fellowship, did you level up on the exp? It's not adding 2 to the displayed number, its adding raw exp equivalent to 2% at your current level. If you level up in between, the remainder you get for the next level will be less than 2% because you need more raw exp.

You mean whether the collection xp caused them to ding?
No, they did not. Both were somewhere between 30% and 40% into the next lvl.

It's not just the xp from collections. I noticed it during the recent bonus xp periods, when I was using Overseer to get some xp on alts.

Most of the time, I'd get the expected xp gain messages. But, sometimes, I'd get 1.495% (or something else just a tick under the expected 1.5% from a 12 hour common task during a 50% bonus).

It would be like once every 2 or 3 rotations, across 3 accounts.

I did another collection on both alts and once again they got 1.920% xp

Have you been doing it in the same zone? Some bug resulting in less exp claiming overseer in certain zones was happening, maybe the same thing.

Yes, both were in the guildlobby. Another one was also in the guild lobby but got 2%