Some challenges not counting properly or at all

Deal damage with Grenades isn't counting in Breakthrough on official servers, however in Conquest or any mode in portal with official rules it counts

Multi-kills of two or more by using explosives doesn't count at all at any modes. 

I killed multiple times 2 infantries, it didn't count at any mode. Killing 3 at a time wasn't possible for me at all. Even exploding tanks with 6 people inside wasn't counting.