Mystery of the Dead Fruit Flies

Wednesday was everything but routine.

In the morning, I had gone to open the balcony door as usual and I could only stare at the sight that greeted me. Half the balcony was covered with dead fruit/ water flies plus a few other random dead insects. Just so that you can have a better idea of what I saw, imagine that you had disturbed the ant nest, all the ants came out but died on the floor. Except that instead of ants, they were flies. 

What happened???
On Tues night as we were in the shower, we already noticed that there were more of these flies than usual. As these flies seem to like damp/ wet areas, we decided to make a bigger effort of drying out the bathroom so that they do not multiply so fast. But on weds night, things had gone back to normal, the flies from Tues had disappeared (probably dead on the balcony).

The few theories that we came up with:

#Theory 1
We leave a small light on during the night and that light had attracted the flies who tried to come in. But of course, they could not fly through the glass balcony door. Therefore, they had hit themselves on the glass, sustained head injury and died.

#Theory 2
Animal migration. It could be that they were flying through the area in a big group, some got stuck/ attracted in the balcony area and decided to die there. But this theory does not explain how they died.

#Theory 3
I had sprayed some baygon in the balcony area on Tues to kill an stick insect on the floor and my helper had removed away the dead insect. But there could have been some baygon lingering around the balcony that killed these flies. But my question is, how can the baygon on the floor kill flies that are in the air?

Can anyone solve this mystery for me?
*There are no pictures as it is just too gross

Anyway, I have kept the balcony door closed the last 2 days (even in the daytime) to keep out all these unwelcome visitors. But because I had to dry the laundry today, I had started to keep it open again.
Every morning now, I say a very short and quick prayer before opening the balcony door. Lord, please no dead insects/ flies/ creatures.

What else kept Wednesday far from routine was:

1. Gmail seem to have lost/ not able to display the emails from the past one plus month. I freaked out as I do not use an email client and everything was online. There was no important emails lost (I think) but how could Google do this to me?!?
I did a quick search online and realise that this is not a new issue for Google except that it is not common. My emails started showing again yesterday, so I had quickly downloaded them all. So guys, you have been warned by me.

2. Installation of Windows 7. With the Gmail incident, I decided that it was finally time to do the upgrade on my lappy. As most of you will know, this is time consuming and not fun at all.

3. Power cuts. Of course, it had to happen more frequently today because it will disrupt the internet connection that I need to install Windows 7. Murphy's Law. Didn't help that today the building's back up generator took its own sweet time to kick in. At about 7-ish, I sat in darkness with my backup lamp staring into space for about 20-30mins.