My subscribers down

[VASIM]

Hi,

I am tech blogger, i was having around 650+ numbers of subscribers for
my single blog, but from a long time it shows only around 160
subscribers. I dont know why my subscribers number suddenly down.

here is the image that shows sudden decrease in my number of
subscribers

http://tinypic.com/r/sfxojq/5

Thanx,

Answer this plz....
VGM