If it says this then it means that your Pokémon have or are the following thing:
- They where brought over from fake GTS's (PokeGTS, PokeGen, Pokecheck....)
This is usually harmless, but like all things after abuse of this will temporary be prohibited from battles.
actually the first reason is it, since you can't break the other rules without using a hacked Pokémon.
The other reasons are:
- Your Pokémon has max EV on all stat
- Your Pokémon have hacked moves for example: Meteor Mash scizor). This doesn't seem the case when I read your description
- This is very rare but if your Pokémon have perfect IV stat and it is noticed by the Random Matchup then you are also prohibited from battling for a while.
( The perfect IV is usually still overlooked but in suspicious actions you can get disabled for a few days to a week)
the 2 points that are marked are usually the problem.
If you know this is the case, then I suggest you do something about it
Hope this helped in a way