If it is whitespot and there are one or two spots still there you need to keep going with the heat treatment (Colin recommends two weeks).
If the tank needs cleaning, do it. If the medication hasnt been in for long enough you can replace some of it - for example if you remove 10 litres of water, medicate with the dose required for the new 10 litres. Then do a large water change and add carbon when the tank has been treated for the full 7 days.