Azaleas

Are you sure it is not a deciduous azalia.?

If it is an indoor azalea, are you sure it is not too warm. They can drop leaves when bought back in if the night time temperature in the house is too hot (should be 45-55 degrees for azaleas)

I presume you have already checked if it has enough water

Re watering. Azaleas usually have ball of peat around them. You need to be sure this is thoroughly wet before planting elsewhere because it doesn't soak up water very easily from the surrounding soil if planted when moderately dry.

All plants change their leaves at sometime even evergreens. Just because you notice leaves falling off it does not mean the plant is sick.I think Fleurdemai has the answer.