they would still have food in their stomach.
My best advice to you is never leave food out for your dogs and feed them once a day before bedtime, unless they are puppies.
I have heard and known many dogs dieing of gastric torsion and the symtoms you describe are scarily similar, except your dogs didnt collapse.
Dogs can go days without food and be fine. They have all the energy they need.

"When I took them lure coursing I fed them a light meal about 3 hours before they ran. They didn't have those symptoms that time."
you shouldnt have done that. Its not only dangerous but it slows a dog down significantly. Your dogs would have ran better on an empty stomach.