Fine ? Really ? With all this artificial stuff ? I disagree.The tank size is fine for those fish. As they grow they will need more room but they have 12 months before that happens.
A young fish (a living being), is already dead so there IS something wrong, and this is gonna last for a minimum of 12 months in the ""best"" case scenario...
Memo : Goldfish can live up to 30 years old if cared properly so a Goldfish that dies this young is abnormal whatever the species.