Alright by far Challenge #5 is the hardest one of them, but I feel that this isn't a skilled based one, so far everytime I have died it's all been caused by one enemy: Flies. I think they are simply too fast for the first shot of a wiz/Loki to catch up with them, they only start dying when the baby is already shooting at something else on another tile, of course this is just a problem on the spiked filled lanes, middle two flies just die when they touch a tower. When one of them reaches the end, you're gonna be praying that one of the lokies' backshots hits them or else you're doomed the next second.
Is it possible to remove them entirely, or at least tone down on the amount that comes from the sides? I think asking to change how fast babies shoot and how they detect enemies might be a tad too much right now, so I'll leave that out of my suggestions for a fix of this challenge.