Thank you for your question. This looks like a severe case of what is called oedema in tomatoes. It usually starts as raised spots that turns into wart-like swellings or growth. The swellings may break open, become scaly and change color.

Oedema happens when the roots take up more water than the leaves can use or get rid of through transpiration. The excess water and pressure in the cells make them rupture. The symptoms appear especially on the lower side of the leaves. Some tomato varieties are more sensitive for developing oedema. If not too severe, the new growth usually recovers when water is more balanced between uptake, use in the plant, and transpiration.

To reduce the symptoms, try to water carefully only in the mornings and avoid overwatering or saturation of the soil. Increase plant transpiration by increasing airflow and ventilation around the plants, in order to reduce the humidity in the air surrounding the plants.