hi,
I just went to Hollywood fish farm in NorthShore, Auckland. I planned to uy the malechite green but they told me if this only happen to female gups, it is more to the water quality problem but not the parasite issue. They also said it happens to adult female after they gave birth and they are pretty weak and could be weaker due to the damage of internal organ caused by the acidic water. I am getting those thinner fish out first to make sure it is not parasite first. If i found more males then I might just go get the malachite green.