Rosie, my RH normal Gouldian hen is sick


I cleaned out the nest turned around and Rosie was in the sun, on the feed table. I just went and gently picked her up and put her in the hospital cage. She didn't even try to fly away. She is in there with a heating pad. I have given her some liquid calcium and she has a vitamin mix in the water. I've seen her eating and drinking a bit but she is basically just sleeping on the bottom of the cage, at the edge of where the heating pad starts (the pad covers half of the cage bottom).
Any idea what could cause this or what other treatment I can give? I have no idea how old she is but based on the size of her chicks compared to my younger hen's first clutch, I don't think Rosie is a youngster (my younger hen's chicks are 1.5 times bigger and they are 2 weeks younger). I've had her and her mate for 7 months now with no signs of ill health. Everyone else in the aviary looks perfectly fine.
Diet consists of seed, fresh veggies/fruit in the morning, eggfood in the evening. Access to eggshells, cuttlefish bone, fresh millet spray given weekly. I also give safe plants out of my garden which is kept organic. I give a vitamin mix in their water twice a week. They are in an outdoor, planted aviary which is dry and wind proof and I worm every 3 months.
Thanks as always
Roxanne (who right now feels completely helpless
