My 460ex mono has two bad columns

[yxz2785]

Hi, I bought the camera secondhand from astromart one month ago and seller bought it originally from Starizona on August 4, 2012. The order number is 5149.
I found it has two serious bad column,  seems it's getting worse compared to 6.22 and today that I took just now, they are all 10 stacked.  The left one is very obvious and getting worse, in 120s dark frame 2 stacked.
My English is bad, hope I explained well.
-5c 7.6 bias


-10c 6.22 bias


-5c 120s dark


Is the ccd chip defective?

Look forward for response soon, thanks

[yxz2785]

-10c 6.22 bias

[yxz2785]

-5c 120s dark