I apologize, as I am late to the conversation. I've noticed with these, it was impossible for me to get certain water spots off the leaves.
The brown tips suggest to me low humidity. Do you provide it with a pebble tray? I saw that you mist with tap water, which I believe could be the cause of the water spots (we have hard water and this happens to me), but misting (or so I've read) is only a temporary humidity raiser. Once the water evaporates, it's back to dry air again. A pebble tray would be a a more permanent humidity "raiser" IMO.
