It takes a lot of preparation for a new foal. Some changes to the house are needed. It is hard to tend to two young pegasi and to prepare for a new foal - at the same time, trying to hide a family secret from innocent eyes and ears... so luckily, kind aunt stepped in and generously offered to host the fillies at her place. Maybe... just maybe... she bit more than she can chew...

With no magic, there is no more common goal for the sirens, and with no common goal, there is nothing holding them together.

And with nothing holding them together, they quickly fall apart.

You only appreciate what you had when it's gone...