I don't have much advice about poor little Cupcake, unfortunately. But I'd like to recommend a feed change. Purina is an alright feed, but it has a lot of fillers and additives that are unnecessary.
I used to feed Purina, but I eventually decided to switch to Kalmbach because my hens stopped laying on Purina (they upped the glyphosates, which can stop laying). It's organic, and doesn't have all those fillers. I first introduced it mixed into their regular feed (it smells so much "tastier" than Purina, too!). You know what they did? They picked around the Purina and ate only the organic Kalmbach feed. They never touched the Purina after that. They've never had weight struggles since (some were over and underweight). They also started laying again within just a couple of weeks. Good feed is important for flock health, and "Big Brand" doesn't always mean good!