User blog comment:Miskos3/Fairy Tail Spring Festival: Special Chapters, Review/@comment-27.106.87.84-20140330072919/@comment-7418318-20140330074857

Now nothing is wrong. Asuka was ill at some point during the time-skip and the parents were low on money to buy medicine.

Juding from Asuka's age, it was likely short before the Tenrou group returned, which would also be the financial low-point of Fairy Tail and would explain their money problems.

Since Asuka was completely fine when the Tenrou group did come back, it's clear that whatever medicine the Connels bought with the money from their memento worked and cured the girl.