brt help raintree sheding

Did a quick style on my BRT tonight and noticed that some of the smaller leaves (darker green so i believe they are older growth) were crunchy... i cut them off to investigate further and they did have a noticeable crunch but did not crumble. At the folds of the crunches they turned a darker...

I have had this tree for 3 years with no problems, however this summer it has struggled. growth has been slow, and this week it has begun shedding green leaves. I have always kept it indoors on my bedroom window it faces east and gets plenty of sun. it has been here since Christmas 2015. I have...