Right click on the mesh where the texture is blurry and select 'Filter photos by point' to see only images covering this patch in the photos pane.
Then select only the 'enabled' photos in the photos pane and right click on them and select 'Filter photos by selection' to only look at photos that may be responsible for the blurry texture.
Optionally (if using pro) right click the middle of the blurry patch and select 'create marker', then highlight this marker in the reference pane.
Now open one of your photos in the photos pane and cycle through the filtered set using page up/page down. The view should always centre on the selected marker position if you created one.
Hopefully the culprit should now be easy to find!
If not, check Tools -> Mesh -> View Mesh UVs to see if the UV map was badly distorted in the blurry areas for some reason. Switch to scaling view to see any stretched areas.