The first part of the commission

Peach Watermelon the Bat Pony and a Seapony O.C. (I don't know her name) give their mother, Fluttershy a plant pot with a beautiful flower. Fluttershy noticed something strange with the plant but accepts it as a gift, but something goes wrong when the pollen from the flower spreads on the three ponies and it does something interesting. They begin to use their diapers, but also de-age to foals. Fluttershy isn't too happy about being a baby again and possibly missing work.

Fluttershy should take a vacation every once in awhile and this is one of them.

And yes, the flower is Poison Joke.