Sudden Death After Limping

Hello all,

One of my Light Sussex hens (just under a year old) died suddenly this weekend. The symptoms were as follows:

Day1: hen limping.....no outward obvious reasons for limp - no signs of bumble foot, abrasion or cut on foot. Hen was still eating and was alert.

Day2: hen not wanting to move; just wanted to lie on ground and take weight off poorly leg with wing. Was still eating though as was food in her crop. Still no obvious reason for difficulty in moving.

Day3: hen found dead in the morning.

I am thoroughly bemused. Until the hen showed a limp, she had been an active member of her flock and showed no symptoms of illness (certainly there were no respiratory issues and she had been laying). Whilst all the other birds in the flock seem fine, one has been acting a little oddly for the past two days (loitering in the hen house (but with no signs of being broody or bullied)) and I am of course concerned about her too now. She did lay a windy egg this morning...I don't know whether that would make her behave a little oddly.

Does anyone have any ideas?

Cheers, Flamingo