Yes, it was indeed oxygen deficiency.
Relying on the "free" seashell coins handed out by the Goddess of Fortune during the counterattack, Leon had bought up most of the oxygen in the valley. The oxygen content in the air of the entire Emerald Valley was extremely low.
Blurred vision, accelerated heartbeat, rapid blood flow, pale skin... all the abnormal symptoms on the Goddess of Fortune's body were severe responses to oxygen deficiency. And even if she temporarily bought "health" for herself, it probably still wouldn't resolve the state of oxygen deficiency.
As for the reason... there wasn't just one Goddess of Fortune in Emerald Valley!
