eek, 5in 30g??? thats pretty over stocked. general rule of thumb with goldies is 15g for the first one and 10g for each after. so 2 should be in 25g, 5 in 55g. they are really messy fish and because they were bred for so long to be small and compact, all of their organs are in places that cause issues in less than perfect conditions.
your ammonia and nitrite levels should be 0. no compromise. if your cycle is complete and stable, those values should be 0 and not budging. if they are not, please add aeration and do hefty water changes on the magnitude of 50% every other day or more.
your nitrAte levels should be under 40ppm. idealistically below 20ppm but i doubt you will ever see that as stocked as you are.
get a liquid regent test kit and keep a close eye on those along with your pH. your pH doesnt really matter as long as it is not extreme and it does not change. a STABLE pH is far more important than an IDEAL one.
goldfish are also notoriously over fed. given they are exceptional beggers and do danged cute when they eat.
feed them goldie pellets once a day. skip pellets once or twice a week for shelled peas. it will keep things... moving along so to speak.
make sure you are doing a 50% water change at least twice a week.
goldfish should live at least 25 years. they have a reputation of being easy to keep and i think that is only because they seem to be easy to replace. if you take good care of them now, they will outlive any dog or cat.