PLEASE HELP - kentia palm

[RT00]

I have a kentia palm which I've had for a few months and has been very healthy and have followed all the advise and mist it once a week and the last 3 week's or so it seems that the leaves are during dark and dry and on some brown spots seem to be forming however the stems are strong, health and green and other leaves are healthy. I think it's root rot but I'm not sure, the roots still seem white, a few brown here and they but no sleep and aren't mushy. It has sufficient draining and a water schedule so i dont think its underwatering but ive had no yellowing of leaves or stem and I'm not sure what to do or how to tell. Any help and advise please