Rainbow Flower In My Lens.. HELP!!!

[nikon90s]

I went out today to take some shots of the sunset but when I put my 70-200mm sigma with my 2X on it It look like there as a rainbow flower in the lens. like a lens flare but a lot of them very small in a flower shape. My D70 would not let me take a shot and the only thing that was flashing on the LCD was Auto ISO. I put my 50mm on and it was fine, I took off the 2X and my 70-200mm was fine. I took on and off the 2X a few times and put the lens on my camera, checking each time and then The strange flare was gone. Also when the rainbow flower was there everything else in the shot was very dark, the flower was about 1/3 or more of the view finder. Has anyone seen this or know what this is or should I just stop taking drugs if I did take them???