Pictures would help. If they are irregular shapes that seem to go through or mostly through the leaf making a thinner almost translucent spot, that can be sun scorch. It tends to happen when water stays on the leaf and then direct sun hits it, making a magnifying glass effect.
But these are indoor tomatoes, aren't they? No direct sun, no sun scorch.
If they are circular greyish white spots with dark edges, probably septoria.
Otherwise, I'd need to see pictures.