When you say bad breathing what do you mean

are they gasping at the top of the tank ?? Have you done any tests

could be your tank hasnt cycled and you have high
ammonia levels which would cause the fish to gasp,,
what are your water parameters

?
With tap water you are putting unwanted things in to your tank like copper , phosphates, ect ect
chlorine and other chemicals that treat the water supply to your house , and all the above will cause inverts to die if copper levels are high , algae blooms from phosphates in tap water , it would be a better experince if you used
RO/di or distilled water would even be better then tap water ,,,,