Why one dog reacting doesn't mean the others will
Dogs process foods differently even within the same household, and buckwheat is no exception. If only one dog ate the cooked buckwheat and the others didn't touch it, their systems weren't exposed to the same potential irritants. This means their risk is effectively zero unless they also consumed some when you weren't looking.
Watch the unaffected dogs for any sudden loss of appetite or unusual thirst over the next day, though these signs would be surprising. Their normal behavior means they're clear.
When group feeding might hide individual reactions
If the dogs usually eat together from shared bowls, double-check that no buckwheat remnants are left where others could nibble later. Some dogs hoard bits of food to eat privately, which could delay symptoms.
Separate their feeding areas temporarily if you're concerned, though cooked buckwheat rarely causes issues unless eaten in large amounts. The real risk would come from flavor additives like garlic or onions mixed into the grain.
Comparing this to raw buckwheat risks
Cooked buckwheat lacks the fagopyrin found in raw groats—the compound that causes photosensitivity in grazing animals. Your dogs would need to consume pounds of the cooked grain to risk even mild digestive upset, unlike the raw form which poses higher toxicity concerns.
Since you're dealing with a prepared dish, focus more on what it was cooked with (butter, salt, spices) than the buckwheat itself. Plain boiled buckwheat is essentially inert for dogs at typical portion sizes.
Monitoring multiple dogs efficiently
With several dogs in the home, watch for individual changes rather than group behavior. Note which dog had the buckwheat and track only that one for vomiting or diarrhea, while casually observing the others during normal interactions.
If the exposed dog shows no signs within 12 hours, you can relax completely. For the unaffected dogs, their safety was never in question unless they find hidden leftovers later.
The full verdict, portion guidance and serving notes are collected on the Buckwheat food facts page.