If you have a flush port where you can screw in a water hose, then flush it that way, use some line trimmer line or something similiar and run it into the weep hole.
I would avoid compressed air, that's just me, I have seen it done, I just believe it packs debris and forces into tight spots, water agitates, loosens and carries debris.
This video explains it:https://youtu.be/7o734ME63u0
If the above works, remember that you had a lot of sand in the water pick up, this may have reduced impeller life. If it were me I would do an inspect of the water pick system, it doesn't take much time and worth the effort, especially if it's close to replacing the impellar as maintence anyways.
If the above doesn't work, I work suspect the impellar.