If you experienced a death while rescaping, it's possible you released toxins into the water column.
Have you tried doing a water change?
Did you get the shrimp from a fellow hobbyist or from a store? If you got them from a hobbyist, reach out to see if they've had any bacterial infection issues. If from a store, you could probably do the same.
If you could post photos of the shrimp, that would be helpful.