I found that they are Invulnerable when in contact with obstacles. Once touching an obstacles along the bottom they follow it to the left are invulnerable and if they run into something on the right they they are stuck and can't move. There is no way out of the mini game except death. So you have to restart if one of the slimes gets stuck. There is also what seems to be a bubble around the player that the slimes run into sometimes. It seams the slimes have 2HP but there is no indication if you actually hit them the 1st them.