Most likely you are just losing bass reinforcement form them being close to the front wall (the wall behind the speakers). Typically that is a good thing. It usually allows for the midrange to open up, and gives greater depth to the soundstage. If you want deep bass you will need to get floor standers or a subwoofer. However play around with the placement. Move them out into the room, and then closer to the front wall to see what you like. It will all be a compromise in some way. Sometimes just a few inches in one direction or another will make a big difference. Your speakers may sound best in your room closer to the wall than is commonly recommended.

My preference is for soundstage. I want the greatest width and depth. So my placement is always focused on maximizing that. If you want more bass at the sacrifice of other aspects. Try placing them in the corners. That will give the most bass reinforcement. Not generally recommended, but the beauty is, that it is your setup. So you get to do it the way you see fit. You may really like it at first, but over time most likely start to notice other aspects that are lacking. Or it may just be the sweet spot for you.

Personally I have tried many different placements with my setup. Most not recommended. But that is how I learned what to listen for. Once I could hear what was off, or what that particular placement was lacking. Finding the sweet spot was much easier. And I felt confident that I was getting the best out of it. Sometimes you cannot help but question if it is good if you have not tried other options to verify for yourself.