New tank syndrome

Question
Appears we were guilty of creating new tank syndrome.  Since we hadn't threw out the old rocks, we have put them back in the old tank.  All four are sick, one is in much better shape.  How should we proceed? Should we put the strongest one in alone now or wait awhile?  Should the strongest two go in?  Should we put some rocks or water from the old tank in?

Answer
Hello,
Put all the water from the old tank in the new one, and also use your old sponge....or put you fish back in the old tank, and wait until your chemistry is right which means, zero ammonia, zero nitrites, and nitrates should be low.  Then when your water chemistry is right, which could take up to 2 weeks, add one fish, and wait 5 days, then add another, and so on, always checking your water before adding another fish.  The water chemistry is very very important.  If you do not go by the rules, you will lose all your fish.  There is no medication for this.  
Check your water, in both tanks, and get back to me please.
Lynda