The little terrors are quite hard to get rid off efficiently. Are you sure you got rid of all of them? Very , very sure? Well you almost certainly didn't because they drop little baby horrors off the base as they move around.
Compared to a biological cure Joes Juice, or kalk is a fix to kill what you see or notice, but if you have a lot you won't get rid of them first time round, and they will seem to rebloom.
It's not magic, and it's not cause Joes Juice is making them breed or anything. It's just the nature of the beast. The moment you stop activly removing them, the ones you missed spring into life-
No shrimps for me, but mishiting some zo's didn't help them (didn't kill them though)