Zebra Danio changing colors

[squirrelrabbits]

I have a 30G tank that had a school of five zebras in it, to which I just added three more that had previously been cycling my hospital tank. Two of the eight now look like they are changing color, losing the purplish coloring and becoming lighter, even golden. Is this normal under any circumstances or doe sit sound like something bad (like velvet)? I have seen no body scraping as of yet but am on the lookout. The tank water has zero AMM and a slightly elevated nitrite lvel (.25). Ph is 7.8.

I wanted to quarantine them but I can't catch them and I wonder if they are sick, should I just treat the whole tank? I have 3 loaches in there with the danios and two dwarf african frogs who were really just visiting from another tank, poor guys.

Thanks for your help.

trish

 

[squirrelrabbits]

I should add that I had put in some salt and a half dose of copper safe as a preventative a few days ago. Might this be related?

 

[WILDER]

http/www.mushi.petfish.net/velvet.html