Trying to save 4 Phalaenopsis - Looking for help

[RossellaNY]

Hello Everyone, this is Rossella from NYC.
This is my first post and my first orchids: 4 Phalaenopsis that are getting worse and worse. They were a present for Christmas, they came in good shape with a lot of green and healthy leaves and flowers but after one week I noticed that there were a lot of rotten roods so I took them off the pot, checked and cut everything was rotten or dry. One week later the situation didn't get better and there were other rotten roots so I decided to re-do everything again, this time changing also the bark with a new one and clean again the roots as better as possible. Today I noticed that in all 4 pots there was mold that killed almost the remaining roots. So now... I don't know what else do to!! Do you think is there any chance to save them?
For contest, my apartment is very dry and even with the humidifier the humidity is not higher than 30%. The apartment doesn’t have balconies and there are big windows on the south side.
Many thanks for anyone that can help.