Save My phalaenopsis

[GoGreen]

I have a phalaenopsis gifted and it was bought from Kroger. It was in full bloom when i received it in March and had some buds it bloomed well and flowers fell off naturally by June. I water my Phal weekly checking if its dry by poking the wooden stick. I have kept it on the window sil facing north. It is in clear pot and has enough holes. i keep them in a plate over stones so that it gets medium to drip water as well. However, one of the leave has turned complete orange, one has become dark blueish black and others have developed blackish spots. I am attaching the pics of my phalaenopsis. I hope it is not dying. Is it some kind of virus that has attacked?Please advise what can be done to save it.