There seem to be necrotic spots with yellowing. You need to check if these spots have concentric rings characteristic of Alternaria. If so you may use a broad spectrum fungicide like mancozeb. Make sure that the pH of water is between 6-7 for best results.
If you have a the problem of cracking in tomato, it can be of two types
- concentric cracking in circular patterns around the stem.
- Radial cracking is a splitting that may occur around the stem.
These may occur due to imbalances in fertilizer (mainly calcium and boron) and water. You may share your contact for more details.