Your Koka azalea is a Satsuki, and the original problem was probably your low indoor humidity. Without seeing it, I can only suspect possible fertlizer burn in addition - that's much too much. I wish I could help you with your odds of saving it in your Colorado climate, but I'm not experienced in bonsai, having only one received as a gift - and it's a pine.

The link provides suggestions for care that seem to be standard for satsuki azalea grown as bonsai

Here is a link that might be useful: Satsuki bonsai

Slow growth and small new growth is desirable in bonsai the last time I checked. Most good bonsai are many years old, some decades old.

Fertilizing azaleas and especially bonsai is not advised. Azaleas need excellent drainage and will curl and turn brown and die if the roots are kept too wet. The container must have gravel or something in the bottom and a drain hole so the water can drain. Otherwise the azalea will die of root rot.