Azalea flowers wilting all at once

I got a large potted plant of azaleas a few weeks ago and now the flowers seem to be drying up or just falling off. I understand that flowers fade but why all at the same time? The first time they drooped I realized it was due to lack of water and they perked up after watering. Now water doesn't help. Is it due to water, soil or just done with flowering? Oh, I'd like to add that its near a hear radiator as that's the only space for it with sun. Please help! 

Before 

Now