A discoloration in the scales is usually a sign of bad water quality. Test your water. If you have not already, now is a good chance to get a water test kit or take a sample to your petstore, they will do that for you.
This is what you should be reading
Ammonia 0
Nitrite 0
Nitrate under 20ppm
Try to keep a temperature above 65 degrees F
Do not do 50% water changes unless its absolutely necessary(if your levels are absolutely bad, they will let you know at the pet store). This can be a shock to your fish. Instead, do 30% water changes every other day until your water levels are fine, then go to your regular weekly or biweekly water changes.
Depending on what it is, is how you will treat it.
Ammonia - you can use a product to neutralize ammonia(ammolock). It does not remove ammonia, it just brings it down to safer levels. 20% daily water changes until your levels are ok.
Nitrate - 30% water changes every other day til you bring the levels under 20ppm