today, i noticed my yellow tang was swimming odd. I did have a bicolor die in the tank which i was unable to find about 5 days ago. now my yellow tang is dead, and all the other fish are swimming odd. fins are splitting. i did a 25% water change today, just tested my new ammonia level and it looks like it is in the 1.5 range. i don't have any more water at present to do another water change. is there anything i can do to stop this progression, or are they gonners. all help appreciated.