You'll most likely need to clear out the nozzles. As already suggested by XPerties, try the compressed air. Be real carfull in inserting any needles, pins, or small wire to clean the nozzles out, as you can enlarge the holes too much to the point that they will not spray a decent stream of water to the windshield.
I bought replacement cowl covers about a year ago, and they came with new squirter nozzles. I removed the old ones from my old left/right cowl pieces to save.
If I can find them, I'l PM you to send them off to you. I'm just not sure where I put them.
Give an answer, they learn for the day; suggest a search, they learn for a lifetime.
2007 F150 STX Supercab (4.6 2V V8), Edge Evolution (87 tow tune), factory navigation radio, tailgate handle backup camera, H-D headlights, Mark VIII 2 speed electric fan conversion with flex-o-lite controller.