gsp have wholes

yes and no. i would do a 10% change every other day for about two weeks, then do 50% once a week or 20% twice a week. and you should get a hydrometer in order to accurately keep track of the salinity levels. constantly fluctuating salinity will stress your fish at the cellular level.
 
Are you using marine salt & how are you measuring it?
 
AquariaCentral.com