Hey @CameronSilburn,
As you mentioned you discovered, yes the quality at the center will be best for such pictures because it is the area of least distortion. As you move away from the principal point, or where the camera's line of sight (optical axis) intersects with the image plane, you will experience distortion, which we attempt to remediate with multiple images via adequate image overlap and the subsequent construction of an orthophoto.
Do you know what image overlap you are using for image collection? Like @CodyBenkelman said, I can't quite make out the blur you describe as much as a difference in coloring/saturation almost. Without adequate overlap (~70% side, ~80%forward, depending on the project), you may have blurring in between image centers as well as along the edges, though.
Similarly, if your photos are taken at different intensities of light (say the sun was intermittently blocked by clouds), be sure to check color balancing in processing options if you want the software to account for it. The behavior may be attributable to different levels of light in the imagery used to create each tile of the mosaic.
Additionally, the tiles are not irregular as you have depicted according to this blur. The mosaic will generally use rectangular tiles in accordance with the aspect ratio of the images used, so it is likely not attributable to seamlines.
That being said, I have no experience with multispectral processing, so these suggestions may not apply.
Best of luck to you,
Josh B
