What's the Name of That Book??? discussion

I read this book series quite recently, and remember most details except the name. It was a bout a family of seven children, each named after a day of the week. Their personalities correspond in some way with the nursery rhyme about babies born on different days of the week. The eldest child is a daughter who was born on a Sunday and is very cheerful. The youngest is a baby who— unfortunately— has gas problems which he uses to communicate. Their parents go missing, if I recall correctly. They befriend a girl who has severe allergies which prevent her from interacting with the outside world.

I think The Problim Children!

Amazon has a preview of The Problim Children (book 3) by Natalie Lloyd:

- https://www.amazon.com/Problim-Childr...