Shrunken comb/tail feathers

I have a Legorn Exchequer hen that has shunken comb and no tail
feathers.Usually her comb is large and red as they should be,but i would say
her comb has shunk to a quarter of the normal size.She now looks similar to
a young hen/pullett.I have noticed lots of feathers about in the last 2
weeks so thought one of them was having there first moult.Other than this
she is eating and doing the usual things.My other Legorn/2 sussex look fine.
Any ideas?
I am thinking something serious,please someone tell me it isn`t.
Thanks Keith


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