Question
I grow under lights. The light set-up is under a window. The window was open when the gardners came and I suspect that when they put down a chemical for the grass the wind blew and it affected the plants. I have lost almost all of my Phalenopsis plants to this. There seems to be a rust like film on the leaves and the base of the plant begins to turn black and soon the leaves die. What do you think the problem might be and is there a solution?

Answer
Dottie, if you have a picture to share, that might be helpful. My initial thought is that your plant(s) may be infected with a tiny mite called a spider mite.  They usually create a film where they have attacked the plant.  While they are tiny, they reproduce rapidly and, because there are latge numbers, they can rapidly suck the plant sap from leavess.  Usually, they first do their damage on the underside of the leaves.  There is a hardy variety of this mite called the red spider mite which may be responsible for the rust-like coloration.  They thrive when conditions are fairly dry. If, in fact, this is what caused the damage, you will need to obtain an insecticide effective against red spider mite.  Repeated sprayings will be necessary because, as eggs hatch you get new generations of mites.  If you can find a systemic insecticide effective against red spider mite, you might use that but it will only be effective on newly growing tissue where it can be taken up by the plant tissues and kill the mites as they suck the plant sap.  The systemic is not a substitute for a spray but may be used in addition. I'm inclined to think that the lawn chemical would be too dilute by the time it reached your plants to be responsible for the damage.  Once  the mites have done their damage, the plant is greatly weakened and its tissues may be exposed to fungal spores and, hence, a fungus infection can occur causing some plant tissues to turn black.  Understand, that this is just one possible scenario but seems to fit with your observations.