Internal Parasite Problems

[ImmortalRav]

I've been dealing with an internal parasite problem. Would it be better to drain the tank, clean the walls, gravel, filter and start again with new water or just keep treating it?
 
I've spent close too 100$ over the past month on stocking with new guppies and they just keep dying. I do quarantine them for two weeks, before adding them into my show tank. They only start to get worse once I add them to my show tank. 
 
Suggestions?

 

[LyraGuppi]

Have you seen what kind of internal parasites they are? 
Is the show tank cycled? What are its parameters?
 
Sorry for the small flood of questions. 

 

[ImmortalRav]

Parameters I do not mess with Ph. Just did a water change the other day and all of the other guppies that I have had before are doing fine.
 
I only know of what type of internal parasites I'm dealing with as they are getting skinny and pooping white strands.All of the females that I got from the store miscarried as well and or only had one or two fry that survived.