worse comes to worse, get a cheap glass tank or... when in desperation last time, I used a pail, put in an air stone,.. and depending on how much lifestock is left, change about 10% of water every few days since there is no filtration system in the pail. If you feed more to boost up your fishes health, then change more water. That's the best I can think up at the moment.
Or you can Call up the LFS that you got your fish from and ask whether they can hold your remaining healthy livestock for you whilst you give your current setup an overhaul and recyle all over again?
where do you get your water from? Have you even tested your water parameters as what the above bros have been suggesting you to do?
Unforutnately you're not telilng us allot of detail other than your fish dying so we don't have a good perspective of the scale of your situation.
good luck.. we have all been there so we know how it feels.