Need to no size of tank in gallons or litres, how many fish and which type, plus water stat in ammonai,nitrite,nitrate, and ph, the spots are they small red pin pricks.
Not the writer of this information.
Red spots on skin can be caused by:
Regarding the small red dot, small pinprick like haemorrhages (called petechiae) can be due to a local lesion, a generalised septicaemia or toxaemia caused by acute viral and bacterial infections.
I would also recommend some daily water changes on the main tank.
diseased fish released pathogenic bacteria into the water, which in turn infect other fish.