Was this on the second round? The enemies gain health and deal increasing damage every round, so even by round 2, they'll take more than one hit from an un-accelerated ball.
Viewing post in smack paddle: bounce ball jam comments
Balls passed multiple times on the enemies without killing them. But I retried it, and this time, 2 or 3 hits and they die. This time, I made a new game, and there was massive lag on level 7, with of course a loooooooot of enemies and 8 or 9 balls I think. But hey, this is a fun game, really !
FYI: I go in the middle of a side, I wait until every line comes to me, I start going down, then I go on the other side with a boost and get all the bonuses, then I start again. Pretty solid strategy :D