That just happens sometimes!
Hard to explain failures are often caused by one or more of over watering, pests (including at the root level), too little soil, or bad soil PH. Symptoms of pests include visible bugs, mold, eggs, or webs (check under the leaves) or a weird smell. PH problems sometimes manifest as discolored leaves.
Also like animals plants have very different levels of vitality, there is strength in numbers!
If you want to try again let me recommend herbs and leaf vegetables. Mint, basil, arugula, lettuce, and mustard greens grow fast and mint in particular is somewhat invasive and hard to stop it gets going.
It can be tough to grow a tomato that looks like the ones at the grocery store without experience and more time and care. There's an art to it.
