I am with King, a bad smell and brown roots usually mean the root system in at least one of the phals are taking place.
Un pot and repot, whether separately or together again, I use a med/large bark and LECA mix to keep it airy and a layer of moss on the top to keep in moisture but not wetness.
Cut off all rotten roots, pour a bit or hydroperoxide water and rinse after 10 sec or so.
And then back in the pot
This is a rather instructional site I came across
Easy Orchids - Re Potting A Phalaenopsis
Hope it helps, keep us posted