How did you reset the tank? Did you kill the biofilter?
First - check water for ammonia ... this is possible an ammonia burn. Treatment is immediate water change. <The higher the ammonia, the more water you need to change out ... make sure you dechlorinate the water, and match temp, etc.>
Actually, a big pwc is a good thing even if ammonia is normal ... you might have some chemical residue from tank cleaning (did you use soap?), that can give you the same kind of picture. I would do a couple daily 50% pwc's. at the minimum. <if you have sky high ammonia or suspect tank contamination, you can do up to 100% water change .... ie remove the fish to a clean container & completely change out your tank water ... just make sure that you carefully match the water parameters (esp. pH & temperature, and salinity if adding salt) so as not to shock the fish.
BTW - how big is your tank/pond?? If you have a big pond, it is acceptable to use an ammonia/toxin binder (like Prime) instead of big water changes in an emergency. However, you would still need to fix the underlying problem that cause the water parameter problems.