If all the specks have just now gone within the last four days you've only just begun to fight.
The life cycle of Ich is such that when the fish have specks, you start to treat. After a few days the specks fall of, not due to the meds or salt killing the Ich at this point, this is just the course of the life cycle. The specks fall to the bottom of the tank and are encapsulated in a protective encasement to the extent that they are totally unaffected by the salt or meds in the tank.
They are now in the substrate producing thousands of protozoans inside the cysts.
It is when the cysts in the substrate rupture, or hatch, after several days of sitting on the substrate, that thousands of microscopic free swimming protozoans spew into the water column, and it is then that the salt/heat method, or Ich medication, has an affect on them.
The free swimmers are looking for a host, but at this time they are vulnerable to the treatment. This process takes days several days, so just because you no longer see specks doesn't mean the Ich is gone, it is not. You must not stop treating during this period just because the specks are no longer on the fish.
It is vital that you continue the treatment for several days after you see the very last speck gone from the very last fish. I would go 10 days past the last visible speck. All the while gently vacuuming the substrate to remove cysts that haven't ruptured yet. They don't all just rupture or hatch out at the same time, so going for several days will take care of this.
The heat speeds up the life cycle, and, in addition to that, at 82 or above the free swimming Ich protozoans are unable to attach to the fish, so reinfection is prevented, unless you stop the treatment too soon.
If you stop treatment before all cysts have ruptured, then when they do rupture, into a tank that is now safe for them, they will make a bee-line for your fish.
They get in the fish's mouth, nostrils, gills, throat, and under the skin but you don't see them. Not until, once again, they start their life cycle and you see the specks once again on your fish.
Cysts that hadn't hatched during too short a treatment period can put you right back where you started.