If the water dish was empty and it is very warm then he might be suffering from heat stress > put electrolytes in the water.
How old is the roo?   Was this "fresh" scratch? (mycotoxin is often associated with old, or moldy scratch and often you cant tell beforehand if this has occured during storage and afterwards dried out) What is the weather like where you are? Do you have pigeons (might be trichomoniasis) > when you look in the beak is all "clear"(no placques or such to see> look at the roof of the beak also)...
>>> Do NOT "squirt" water or any other liquid into the beak!  They have two "holes" > one leading into the crop and the other into the airways > poultry do not have an eppiglottis to close this hole as mammals do and when you squirt water into the beak it will often go into the airways!   Dribble along the beak... offer freechoice yogurt or watermelen and moisten their feed (with cooked oatmeal for instance) if  dehydrated.