Why are the leaves on my orchid dying, when the flowers are blooming

You should pull your plant out of it's pot now and check the roots to see if you still have any live ones. Usually by the time you see the leaves dying most of the roots are already gone. The dead ones will be pretty obvious because they'll be mushy and black. Live roots should be white or silvery and have the consistency of styrofoam. They will also often have a green growing tip. Remove any dead roots and the dead leaves and repot your orchid in fresh bark chips.

Stop watering so often. You should be feeding every time you water, about every three-four weeks. It's best to use a liquid orchid food at half the recommended strength, but if you already have Miracle Grow you can use that. In between watering, mist your plant lightly every few days or so. I use a quart bottle with one drop of liquid Miracle Grow in it to mist mine. Be sure to mist the leaves as well as the root zone and any air roots. After misting place your orchid in an area where the moving air can dry off the leaves fairly quickly, like near a slow-moving fan.

When you water your orchid make up a bowl or pot of warm water with the plant food in it. Put your orchid roots into the water and let them soak for about 15 minutes and then lift it out and let it drain completely. Since you only have MG plant food, you can use the runoff from your orchid to water your other house plants.

Don't feel too bad if you lose your orchid, over watering is the most common mistake folks make. I've killed a few orchids over the years myself.

http://homeguides.sfgate.com/orchid-plants-leaves-turn-brown-dry-70396.html

https://gardening.stackexchange.com/questions/14598/are-these-orchids-dying-they-are-flowering-but-the-leaves-are-turning-yellow

I love orchids! How many leaves? If you give the leaves a tug, do they pop off? You shouldn't prune orchids when they're in bloom. You can cut the leaf and treat your plant with a fungicide or bactericide(spelling). I often need to do this with my orchid. This is to stop the bad stuff from spreading to the rest of the plant. Cold wind or being too hot can do this. Do you have a picture? Good Luck!

Are you over watering It? That happened to my daughters while it was flowering. We think that someone was watering it behind her back because she hadn't watered it in two months and was always soaking wet.