Phalaenopsis: leaf disease? Wet roots?
 

My supermarket phalaenopsis bloomed last year in the summer and I left it in the bark mix and aerated plastic pot within an undrained ceramic. [I forgot to take it out!] New flower spikes appeared over the fall and I moved it from behind a lacy curtain by the window to a table 5' from the window with some partial full afternoon sun in the winter. Yesterday I did my weekly light watering [without first checking for dampness] with a dilute "Miracal Grow". Today I noticed one of the three flowers only about a week old had dropped.
I inspected the plant and found a leaf with a major blemish and a second leaf with a blemish starting. I cut out the two bad sections. First is that the correct action, or should whole diseased leaves be cut off?
The photo shows the damages. Can you diagnose?
Then I saw that the roots had driven down through the plastic pot's bottom drainage holes and were in 1/2" of water. When I cut off those bottom roots I could lift the plant out for repotting and found most of the bottom 2" of "stem" and roots were rotting in the damp bark. I sawed off the bottom 2" and some other rotted roots and repotted in a wider aerated pot in the sphagnum moss mix I bought. Is the plant on its way out after such radical surgery? If not, what care is needed during this recovery stage. [It has two flower stalks with buds.]

Do you have a floorboard heat below the window? Were those leave touching the ceramic pot at all? Was that leaf touch the window?

That leaf is not diseased, it's sunburned.
Joann

I agree, that's sunburn. Winter sun can be deceptive, and will still burn a plant that has not been progressively adjusted to the light.

As to the plant, it shouldn't suffer too much from the 'surgery', as long as there are plenty of other roots left, which you don't mention.

Sun, surgery & wet roots
 

Thanks for the replies. Some comments in response.
The large picture window 5ft in front of which the plant was sitting DOES get strong winter sun for a few hours each day. I've moved it behind some tall sun-loving African Violets to get more glancing, speckled sun.
There are a few surviving roots in the new sphagnum moss and above it. I've started to lightly spray the visible roots each day to keep the plant going. Is that OK? Continue with weekly watering [well-drained pot]?
The evening room temp is 64 and day temp is 68 [plus sun warmth]. There is baseboard humidified forced air in the room, but not directly on the plant.
Was the "rot" due to the roots soaking in water? Having sawed off the rotted central leaf "stem" is there any first aid for that?
I loved that this store-bought 6-leaf phal had two flower stalks last year and sent out 3 new ones this year!

If this plant is in moss I don't think I'd spray it everyday, you're not going to get much air to the roots if the moss can't dry and will have a rot problem again. How big of a pot did you use? Can you post a picture of the plant?
Joann