Question
I have a  Phalaenopsis that was blooming incredibly in April. It finally dropped flowers and I followed instructions to cut back to the second or third visible junction in the hope that it might bloom a second time.

I followed the advice of my florist and sprayed everyday. She started getting sick when her first beautiful leaf turned yellow and died. Now the other two leaves are yellow in spots and are definitely unhealthy.

I keep her behind a sheer curtain and a heavy linen curtain and water only when the surface dries out.

Is there anything I can do to ward off the fatality of this plant? Any help is deeply appreciated.

Answer
Your phalaenopsis needs repotting.  When you unpot it, you will find several mushy roots.  This is because the potting mix has broken down and not enough air is getting into the potting mix.  When the mix breaks down it retains more water. So, while the surface seems dry, further down in the mix, where must of the root mass is, it is constantly wet.

Buy a hobby bag of orchid potting mix and have it ready when you unpot your orchid.  Discard the old potting mix and clean off the roots.  You will notice that some are really "mushy".  These are rotted roots and no longer provide nourishment to your plant.  You need to cut those off. Retain all of the solid roots as these will support new growth.  Repot with the fresh mix in a  pot that will comfortably hold the new root mass.  If there are sufficient good roots remaining your plant will recover and grow new leaves but it will take several months to bring that about.  Your light is fine but keep your watering down (misting is fine) until you see new growth emerging.