In the videos, I am hearing rales (crackles or rattles) and some sneezing or snicking. How does the crop feel? Empty and flat, full, puffy, hard, or doughy? I would suspect a respiratory infection. Sometimes a crop that is not emptying overnight can be full and liquid may come up into the airways. But with a respiratory infection, mucus draining into the airway from the sinus can cause the rales sound.
How is the ventilation in your coop? Is there any ammonia odor from droppings, a lot of moisture or spilled feed, or mold? Dust in feed can also irritate the nostrils. Do you see any bubbles in either eye, swollen eyelid, or drainage from the nostrils or beak? Respiratory infections can be virus or bacterial, and sometimes from mold fungus. Have you added any new birds recently?