I have raised beds with 8 different strains of tomatoes in there and only one is showing this yellowing of leaves, slowed growth and starting to curl. Can you tell if this is a disease or a deficiency?
More likely a non-lethal dose of glyphosate, the active ingredient in Roundup & similar products.
And yes, it could affect just one plant. Depends upon where (how close to the plant) the spray was applied; whether the plant was shielded/protected by something; how high the pump pressure was; how much spray turbulence occurred; and the breeze, if any.