Maudey, our Gingernut, isn;t well at all. Any advice would be most welcome.

Symptoms -
She's stopped laying totally. They went soft shelled for a while and now there are no more.
Hunched appearance - she just sits in a corner in the garden with a hunched look.
Skinny ribs. She is still eating a bit - it's hard to monitor as ours are completely free range so just because the food tray is empty doesn;t mean that they've eaten it. She used to eat voraciously though, and she's totally gone off sweetcorn, their evening treat. She seems to be drinking more than usual.
Very unsteady/wobbly - she can't really jump up steps like she used to.
Messy bum. It seems to be congealed egg rather than poo all over her feathers around her bits - her vent itself looks fine.
Moulting.

We've given her worming pellets, and the house is regularly mite dusted. It shouldn;t be old age - she's only 1.

Any advice very very welcomed - this is all quite distressing.
Thanks, James