Can feed change chicken color / make a chicken sick?

[puffypuff]

The original owner of my chicken had said she was 4 months old. I've been feeding her pellets (according to what a store manager said I should be doing) and she has been changing ever since. Her feathers are now a beige color and all her tail feathers are shed except one. I've yet to see growth of a new one. Otherwise she acts normally. Should I be worried? Am I making stuff up? I get so paranoid sometimes about my little baby. : (

 

[Twistedfeather]

Corn is the only feed I know changes color. What you do is mix the two feeds to shift then after a while then take out the old one. T

 

[puffypuff]

Corn is the only feed I know changes color. What you do is mix the two feeds to shift then after a while then take out the old one. T

Is there a specific feed I should be giving to younger chickens? : ( I'm worried she is younger then 4 months and needs something else.