It sounds to me like your fish are suffering from "old tank syndrome." This happens when someone does no water changes, only top-ups, for months or years and then suddenly does a significant water change. What is coming out of the tap is so different from the water in the tank that your fish cannot handle it. Then, you get a death or two, and the scene is set for a mini-cycle. Ammonia and nitrite spikes lead to more deaths, and next thing you know, the tank is spiraling. (Especially if you knock back the filter bacteria by throwing out media, rinsing with tap water, etc.)
Do not respond by suddenly doing a bunch of big water changes. Instead, do a long series of very small ones over the next several weeks. Dose, but don't overdose, with Prime daily, if you must, to lock up ammonia. (It's actually a temporary conversion of ammonia from one form to another. This helps prevent injury to fish, but doesn't keep plants and filter bacteria from utilizing the ammonia.) Add an airline/bubbler to increase oxygenation. Using Seachem Stability can help (re)build the filter bacteria. The nitrates will slowly come down, TDS will drop, etc. and your fish should easily handle the slowly improving conditions.
Once the tank is stable, please start doing regular water changes, preferably weekly.
Btw, fish jumping out of tank is often a sign of poor water quality. I suggest that you also test your water frequently until you know, absolutely, that levels are good, fish are healthy, etc.