bobaguppies

I might be paranoid or overthinking that animates have sold me sick guppies.. it all started from February 4th when I bought a bag of female guppies. The tank looked vibrant, then the week after a guppy died. I thought it was complications from giving birth cause a couple of them came to me pregnant. But from there every week I start loosing 1-2 of them. It's all from animates, I got worried that something was wrong with my tap water (maybe it was double chlorinated and I didn't know?) but it didn't make sense as I have 6 tubs of aged water running for water changes and just to be safe I'll add some prime. I also bought RODI just to be safe during this but nothing changed. I religiously clean my tanks every Sunday and do a 15% water change, before it I'll do a test and Ill also do one after (I know I don't need to do this extra steps but I just have a major OCD so everything needs to be 'perfect'). All of my other tanks are fine, this is just from one specific tank for female guppies. It's been 6 weeks, I had 12 female guppies and now I only have 4 (one is going through the same problem. They would have normal looking bellies and couple days before they die, they would get very very skinny for some reason). I've tried what the staffs have recommended me, salt, pimafix, melafix, meth blue nothing worked. Im at my wits end as all im seeing is a floating fish every Tuesday or Wednesday (is this a coincidence?). Idk what to do, I regret introducing new fish in the tank and should have been happy with my originals, they're still surviving but I think whatever it is in there, it's getting to them soon as a few of my originals are starting to show signs. Did anyone go through this??? Should I just cull the rest of them? It is sad that they're going through this and I can't do anything.