Carol, my mandevilla also looked like it wanted to start having yellow leaves, and I was ready to give it some hard pruning, but then that bud showed and bloomed, so it is getting a temporary reprieve. Maybe will wait for that bloom to wilt.
I find the Brassia ones quite water needy. My first Brassia, Brassia Rex bloomed nicely indoors last June 2010, but I underestimated its temperature needs, in short killed it during winter. My bad, that really taught me to be mindful of temperature as well.
This current Brassidium was a rescue last early winter 2015. It started perking up when I finally brought it out in Spring, where I can freely water it often and gets as much air flow it can. I am really happy it gave a 2nd flush of blooms this year, so surprised it did!
