Diseased tank?

[BigLou]

If anyone reads up on my previous posts, I've had a sick platy and two sick guppies in the past week. I put them in a hosipital tank, but I'm worried that there's something wrong with their water in the original tank. I tested the original tank and everything seems to be ok. (Nitrate-30ppm,Nitrite-0pmm, Hardness-75ppm, Alkalinity-0ppm, pH-6.8) The question is should I take down the whole original tank and start from scratch, or would pwc everyday or every other day be okay. (I just did a pwc last night after I tested the water with parameters above).

 

[WILDER]

As long as you have not had any contagious deseases in the tank like NTD, I wouldn't strip the tank down, just do a few more water change, and maybe add some melafix to the tank.