Califishguy is correct, nitrite and ammonia would be 0 in a cycled tank. the tank doesn't have proper bacteria to deal with fish waste, and the buildup of chemicals like nitrite will kill the fish. Your best bet would be to put the fish in another tank for now, or if you don't have another, set up a 30gallon plastic bin with fresh, dechlorinated water and a filter/heater. Put the fish in there and do a 100% water change on the 75, also clean out the filter good. Then Buy some "Dr. Tims 1 and only", or get filter media from a seasoned tank, and put the fish back in with that. That should allow you to bypass the 4week-ish cycling period.