Japanese pieris dying? Help!

[BellBon]

Please help I am new to Bonsai. I got this Japanese Pieris back at the beginning of the year and had it outside on my porch all spring/summer long and it was thriving! As fall temperatures are dropping more and more everyday I brought it inside. Every since I've brought it inside it's leaves are turning brown and I don't know why.. I placed it directly across from a window so it can still receive some sunlight and I haven't done anything different when watering..
How can I help revive my bonsai?

 

[Pixar]

Look like some disease has hit , I would suggest de-foilate and decrease watering ( put back outside etc...)

 

[penumbra]

It needs to be outside. I believe you are killing it with kindness.

 

[BellBon]

It needs to be outside. I believe you are killing it with kindness.

the temperature is suppose to be in the low 30° every night this week, I didn't want it get frosted that's why I brought it inside.

 

[penumbra]

It is an outdoors plant. It wants to get cold and go dormant. Unfortunately I think its done.

 

[RJG2]

the temperature is suppose to be in the low 30° every night this week, I didn't want it get frosted that's why I brought it inside.

They are hardy to zone 5. I don't think you need to worry in TN.

 

[Stormwater]

I’ve got a gorgeous one here in MD. It winters outside. It doesn’t like strong rootwork. Looses 10-20% leaves in the fall.