Chicken 'stress'?

[Sozoed]

We have a Buff O. that has had diarrhea recently, and her diet hasn't changed at all, so I began researching some causes for this and read that chickens can become stressed over minor things. Wouldn't you know it...bright lights is one item listed as a chicken 'stressor' of which diarrhea can be symptomatic.
We have recently put up a 100 watt lightbulb in the coop to continue laying through the winter. Could this really be causing our Buff to have digestive problems?

 

[clairabean]

It could be, but keep an eye on her. It can also be another hundred reasons.