I think you should take action asap. Pump your tank out (if you haven't already done so ) Make sure you have a tank output baffle to prevent floating scum from getting into your field. Pour Septic Seep or equivalent into your D-Box followed by 30% hydrogen peroxide a few weeks later. Both of these products help to clear the septic field.
YES start adding bacteria to your tank, such as Roebick K-37. I have had good experiences with all of these. See my cliff notes with photos here. http://tinyurl.com/Septic-Solutions
I am sitting on the fence for a bubbler added to the D-Box, as I'm still testing Roebick products. I have also not jetted out the laterals yet. Maybe this summer, I also want a riser added to my D-Box to make access easy.