Thanks. i did cycle. Thought 2 guppies & 5 WC would be ok. No plans to replace them. Maybe that’s the issue, the lack of volume.
How could you cycle when you were unfamiliar of what 'water parameters' meant and didn't have a test kit?
Obviously, we now know that volume isn't the only problem.
Moving (rapidly) forward...
Any ammonia in the water is not only toxic for the fish, it burns their skin and gills.
Normally, large water changes aren't recommended, because the change in water quality can stress the fish. However, clean and conditioned water will be infinitely better than water with ammonia and nitrites in it. (I see you're yet to give us your nitrite and nitrate readings).
This is essentially an emergency rescue mission, trying to save those poor fish you currently have, as quickly as we can, so hoping to reduce the long-term damage caused by exposure to ammonia and so forth.
Fortunately, farm-bred fish are often a tad more resilient than their wild-caught cousins and you might have more survivors than you first thought.
You yourself are also on a crash course on the nitrogen cycle and basic aquarium chemistry and, hopefully, at the end of this you'll know exactly what you're doing. The bigger the mistakes, the greater the learning opportunity.