My new fish

[SMOOOZZZ]

I'm still new in being a fish owner. I has two other tiger fish & another cichlids fish. They are healthy & happy. This morning my levels of ammonia were zero and the nitrate & nitrate are also at zero. Did couple of water changes last month due to nitrate levels a bit high. Well today I bought a tiger fish at Petsmart and he's dying, one of his eyes looks like is gray and his skin looks horrible and will be dead in about an hour. What did I do wrong? What should I be looking for? And can my other fish get sick from this dying fish?

 

[The boring name]

Probably he was in a poor condition when you got him and the trip stressed him too much u could always use that 15 day warranty tho and I would take him out now and change him or return him back to store b/c he could infect other fish