Phalenopsis dying (mouldy aerial roots) - help!

[geob]

Hi all,

I am baffled with a relatively new Phalenopsis I got given as a present - I have had it about 7 weeks now and all was good at the beginning; It came in one of those double plastic pots, where a little string dips into water and the water gets transferred via that into the soil.

The guy who Owned the shop initially watered it from the top (water went over some of the aerial roots - and we did the same the 2nd time); since then we have just been topping up the water in the large pot however.

The problem is that I get a whiff of mould on the top of the soil and some of the aerial roots look like they have gone mouldy too. The buds have dropped off in the last week and the 4-5 remaining look like they will follow soon. It has also dropped one of the bottom leaves.

Is there anything we can do? Have we made some mistake? I see most of the roots are green, so I don't understand what has gone on. The orchid is inside, temperature steady about 18-20 C and not in an overly sunny spot.

I am including some pictures too to give you an idea...

Thank you!