Goat dewormer (fenbendazole)

So I've got a 20gal long with maybe 100-150 shrimp, I noticed planaria on the glass so I dosed some goat dewormer from tractor supply. I did 3 drops mixed with a cup of tank water, 6 hours later I did 4 drops, 8 hours later I did 6 drops but turned off the filter and went to sleep. 9 hours later I did 6 drops again but turned on the filter.

Everyone is still alive, pest snails, shrimp, and planaria.

I have a hob filter with a coarse sponge on the intake and a bio filter that looks like a bunch of sticks in the hob. Also I have two bubblers. Substrate is Bio stratum, and I have an almond leaf and three pieces of wood.

Gh is 8-10, kh is 2-4, TDS is about 200. I use ro water with shrimp king remineralizer. Temp is about 73f.

What am I doing wrong? So far it's been between 30-36 hours since the first dose. I've read that pest snails should die along with the planaria.