Rescue! Vandas roots black and leafs drop

[kaarthiik]

Hi All,

I have found some black area around the roots(at there start) on my few big Vandas.
When I noticed on a fat root, I have used a dab of peroxide on it thinking of fungal infection.
Now all 3 fat roots became lean and dry and black. Please see the pics and guide me.
I see similar things it 2 huge vandas and one medium vanada.

And another big worry is they are dropping leafs fast!

I was watering around 3 times in the morning (between 7 AM to 10 AM) and the weather is very hot around 43 degrees centigrade outside, and in the Vanda's area I was able to maintain 30-32 Degrees centigrade.
Humidity on average of 50 to 60

Please help!