Sera Nematol - Needs Redose?

[Vin Swords]

I have used nematol successfully.. 6 weeks ago. Even though it was said to redose in 3 weeks time. But I didn't as I learns cammleus worms are live bearers.. Now some of my fish have White poo.. Have I screwed things up?

And I didnt do 80% waterchange.. Thought 40% is ok and went with it.