Hi, I know you are in panic mode but stop adding all that stuff!! If the Nitrites and Amonia are off the scale then that's what you have to concentrate on. Your older fish may be able to tolerate the high Nitrite but most fish can't. I know you said you cycled your tank but quess what, it either started again or didn't finish. Best thing to do is at least a 50-60% water change. Make sure you use RO, get it from the LFS if you can. If you use those water conditoners then make sure it is a good one and airiate the water for 24hrs before using it. You may have to do one tank at a time and move the fish around to accomodate them while you do this work. I don't think you will corect the problem with additives. Your PH won't stabilize because your water quality is bad. It sounds to me like the tanks cycled but didn't have enough nitrafying bacteria to keep-up will the load. You will need good filters and good water flow to keep the tank healthy after that. Just my 2 cents worth.