Shard/Spark Bug or...

[KhaosMistress]

So I was playing an elemental earlier, and he had Shard of Power active, along with 2 Sparks. No other buffs present, so the sparks had 4 attack and 1 health each. I used a Lightning Storm on one of the Sparks and the hero, but the 2nd Spark died as well? I know that for every other Spark in play, each spark gains +1 attack and +1 health, so when I killed off one Spark, shouldn't the 2nd Spark have stayed in the game with 1 health still?