It's time to replace the bark chip potting medium, but not until it has finished flowering.
Trim off all roots that are not plump, as Daisy described and carefully remove all of the bark chips that are clinging to the roots. Get a nice terracotta Orchid pot if you can find one and use a packaged Orchid mix. The pot should be just large enough to accommodate most of the healthy roots snugly. Fill in the spaces around the roots with the Orchid mix and water it thoroughly.
Phalaenopsis respond well to root pruning and a fresh start in a fresh potting mix. However, it will recover slowly and probably will not flower again for at least another year.
