Hi Butterfly and welcome to Orchid Board
It could be as simple as getting the wrong orchid mix. Either poor quality or for the wrong type of orchid.
I made the same mistake with my first orchid. It grew wonderfully for 2 years and I had ventured to buy two more... when I decided to repot and then it went downhill fast (good news is I managed to save it with the help of the guys here and it has just put out it's first spike since then).
I just could not understand what I had done wrong for a long time, and when my second two started to follow it after they were repotted I was convinced I was missing some vital step in repotting, you may even find posts here on the OB archives where I was asking... "what on earth am I doing wrong".
Anyway, the problem was the orchid mix, I am certian of that now. It was from a local garden center and it was too degraded before I even started. The problem is that it has often sat arround a long time in a garden center and even when new, the ones they sell in garden centers are usually too dense for Phals as garden centers do not distinguish between the best medium for differnet types of orchids.
From your description of the medium smelling, I am 99% certain you have the same problem.
I now only use orchid mix from reputable orchid sellers (or reputable orchid accessory sellers) and I've not had a problem since. They tend to sell different mixes for different orchids and are much better qualtiy. You want to make sure bark for Phals is all distinguishable pieces of bark... nothing broken down and almost soil like. The size you use can vary, but it should always be an airy and 'pieces' not 'grains'.