About a year ago I split my Brassia into two and the plants were fine and thriving until about a month ago. I admit I had been neglecting to water them every week but they were still green even though their psudobulbs had shrunk. I thought it would be a good idea to water them more(once a week) but they just turned yellow and started to lose their leaves. I thought they were looking better but then I went out of town and left them in the care of someone even less skilled and when I came back one of them was dead. I examined the remains and from what I gather it's root rot but I'm unsure; there were some tiny black spots that had been there since I got them;I just want to save my other one. Please take a look at the photo.
Your plant is from the Orchid family and as far as I remember they like cooler conditions, I cant help you with any special watering tips other than to say from the info you have given, you have over watered these plants, any orchids I have cared for like a humid atmosphere therefore to achieve this I would mist the foliage every few days but only water when the foliage tells me it requires this and you can tell as you already discovered by lack of care is, the foliage will begin to turn a pail colour, or IF as I do, touch /feel the foliage, it will be softer rather than nice and firm/plump, there is special soil for orchids and it might be a good idea to buy a couple of bags from the garden store, it is not expensive but it is mixed with all the right ingredients and you should not need to re-pot again for another couple of years.
The little black spots are normal on the roots, at re-potting time I always trim off all the dried roots and your look like there are lots (they are empty straw like) if you feel them and then feel a healthy root you will see the difference, cut the dead ones off even IF they are attached to a healthy root, just cut the dead bits off, then re-pot into new growing medium, don't water for several days but mist the foliage, after a week, start your watering regime and mark down the date so you don't over water again, NEVER leave the pot sitting in water or the root rot you have discovered will return again.
I think there is an Orchid Forum on the site that will be far more helpful than I have as I can mostly only tell you how I do things learned over the years but maybe this wont be the professionals way. hope this helps you out.
P.S. the garden centers usually have leaflets re growing /caring for orchids and other plants that grow indoors so ask next time your there or read one of there books that are for sale, they give pictures and tips also. Good luck. WeeNel.
Root rot in orchids is generally exhibited by slimy , black or dessicated roots. But, it looks like your brassia has expired at the crown and is probably gone. You can try repotting and misting, but I am not sure you will be successful.