I had a very similar experience with my speakers. Originally they were around 2" from the back wall the wall and got a great bass response. However to free up some desk space, I recently put them on mounted wall stands (which brought them as far form the wall as your speakers) and the bass practically disappeared.
I'm using IK Multimedia ARC 2, so after taking new measurements it sorted it all out by boosting the bass a fair amount.
I know that some HiFi speakers are actually designed to make use of the wall behind them for bass, but I didn't think this was the same case for studio monitors... maybe it is for some, I don't know. My speakers certainly needed a bass boost though after moving them away from the wall.
I would recommend ARC 2 though (or some similar speaker measurement software along with a hardware stereo graphic eq). This will allow you to compensate for various frequency responses.
The angle of your speakers did catch my eye on your photo though. It looks like they're angled so the crossover point is just between your querty keyboard and monitor, whereas it should be where your ears are. I'd expect them to be angled to hit your ears around the middle of your chair - maybe it's just an illusion of the photo tho.
M.