[Bug] Spells not working on ladder

My friend was playing ladder at Challenger II using a deck with fireball and snowball and snowball and fireball weren't working....like she threw snowball at two baby D and the baby Ds neither lost any health nor got knocked back. Then as the same baby Ds crossed the bridge she threw a fireball at them and they neither got damaged nor got knocked back. Then a little while later she used the fireball and snowball again (on different troops) and again they didn't work. The very first time she used snowball in the match though it did work. Hey opponent was using mirror if that matters.

Does anyone know what's going on with this?