I have yellow spots on some of my tomatoes.

It doesn't look like a tomato disease. It looks more like splashes of water that have burnt marks into the skin of the tomatoes. This can happen if splashes of water are on them while sunlight is on them. The tiny drops of water act like a magnifying glass concentrating the sun's rays & burning them into the skins.

The only way to avoid it is not to water them when they are likely to have the sun on them.