HELP! Instructions for using Blue Planet Multi-Cure

[Pisces68]

I've had 2 swordtails die from what I suspect is Velvet Disease. I've done a 50% water change & added Blue Planet Multi-Cure. It says to repeat treatment every 3 days with a 25% water change. The exact instructions say "A partial water change (25% of capacity) is recommended before commencing treatment and every third day thereafter before retreatment until cure is effected." What I'm unsure of is do I just add more Multi-Cure to the top up water & then add to the tank, or do I treat the entire tank full again & again every 3 days?
I'm only using half strength because I have 6 neon tetras. I've removed the charcoal. It's a 50 litre tank also with 1 fighting fish, 2 swordtails, 2 Corydoras, 1 sucking Catfish, 1 Bristlenose. I added 4 new Swordtails to my main tank on Xmas Eve, one dying a week ago, one dying today, so I'm guessing they had the disease when I bought them, the other two seem fine so far & none of the other fish have any symptoms either but I'm treating the whole tank as a precaution. And how long do I treat for???
I know now to quarantine new fish for a few weeks before adding to my main tank, but I'm new to all this.

 

[libertybelle]

According to instructions you retreat every 3 days with water changes in between. I read that as treat the whole volume of the tank after the day 3 water change.

I’ve never used this medication before though

 

[Pisces68]

Yes I thought that Im about to change some water & add more now, its really faded. Thanks

 

[libertybelle]

Many chemicals break down in the water over time so that makes sense. Good luck. And do check your water chemistry.

I don’t know what is in that medicine. If it’s an antibiotic or something it may have crashed your cycle.