Exceeds giving massive exp and dragon kills

Earlier I was farming exceeds/vulcans to get some exp, after a while of leveling I had gathered a bunch up and used Holy Nova (which usually 1 shot the exceeds with white drive on) and randomly got like 10 levels from one group of them. I scrolled up and it said that I had killed dragons, and three of them. The exceeds also did not die in one hit when I used holy nova.
I went into the area close by and killed 1 more exceed and got two levels, but that might have been from all the extra exp I had.
Several minutes later I went back to the same area I was in and killed a couple exceeds and it said I killed another dragon. I believe the exceeds in that area might have gotten bugged somehow, as I killed exceeds in another area and nothing strange happened.

That's a cropped image of what it said when I killed the first group of exceeds.


I dunno if you want me to post the area where it happened here or not, but I haven't went back over there since.
In the area around there there was also a seemingly bugged exceed that never moved when I walked by, not sure if that was causing it or not.
But, I can show the area in game/tell you here/make a video if you'd like.



EDIT:


This only seems to be happening to me, another person was killing exceeds in the same area and weren't getting them. I also was killing exceeds in another area for a bit and got more dragon kills after a short while.
I want to level up but I feel really bad when I get a whole bunch of levels for free.


EDIT2:

I think this might have something to do with aoeing several (7-8+) exceeds at once. It seems to happen when I do that, but it's also happened when I kill only one or two.

EDIT3:
I noticed when I use the holy nova on the exceeds and I get a "dragon" kill the holy nova only hits some of the exceeds instead of all of them. Like I hit 2 of them and the other 3 don't get hit

EDIT4:
I believe it has something to do with Holy Nova, as I don't believe it happened with any other skills, and when I had a friend kill a couple exceeds with Holy Nova he also got a dragon kill.