I am so sorry for your loss.
Is it possible they are getting into something toxic or poisonous? Herbicide, pesticide, lead shot, peeling lead paint, metal, rat poison, Styrofoam...?
With this sudden onset, I can only imagine it was brought on by something that changed in their environment.
Is your feed high and dry at all times? Is there any possibility it could be moldy or rancid?
Other than that, purple combs and sudden death are usually indicative of heart or liver failure or some circulatory issue. Sometimes, it can be caused by a bacterial infection they've had their whole life or something hereditary.
Did you happen to perform a necropsy on your rooster? At the risk of sounding clinical, if your hen passes, I would recommend sending her in for a necropsy... You can get information about where to send her from your local vet. They will be able to tell you what caused her death, and at least give you answers to formulate a plan moving forward.
Do you have her isolated? Can you monitor her eating and drinking? How are her poops?
Again, I am very sorry for your troubles.
MrsB