when fishes are infected with parasite like ich , they will secrete some film of layer of coating ...
hypo is one of the most effective way in curing ich , though tedious .
when administer properly , apparent white spot will be gone in at most 5 days , according to my own experience. but full treatment might last for 6-8 weeks
maybe u can tell us your procedure in introducing hypo treatment and some parameter like pH ,KH, and by the way are u using a refractometer or swing arm hydrometer?