Stopped Paraguard started Cupramine

I after a little over a week maybe I was not patient.  I kept seeing more and more parasites on the blue tang after the therapeutic level of paraguard was in the tank.  So now I am using the Cupramine copper at a lower level.  Before the fish got really ill at about .5 to .6 copper level.  Apparently the crypto is eradicated at 0.25 to 0.35 mg/L but recommended you keep it at .5.  I am going to stick to .3 mg/L for 28 days if at all possible.  It states 14 days on the bottle but I have heard from tech support at seachem you should aim for at least 21 days.  If doing a full 28 though that should span the length of the life cycle of the parasite.  Wish me luck as last time I did this 2 fish stopped eating but that again was at .5 to .6 so keeping it lower should help.