Since no one answered, I will give it a try... Hard to say. It doesn't entirely look like wilt to me, but could well be some disease, possibly septoria.
But I think it was vulnerable; it looks like it never was that vigorous to start with. It looks like you are trying to grow it in a pot on a balcony, high up on a building in a big city. It is commendable to want to grow something you could eat, even in those circumstances, but tomatoes aren't the easiest.
The plant has very long internode spaces (stem distance between one leaf node and the next), suggesting it isn't getting enough light. Tomatoes need at least 6, preferably 8 hours of direct sun a day. I can't really see the pot, but from the bit showing, I'm thinking the pot is too small. One tomato plant should be in at least a 5 gallon bucket size pot. And I can't see where those stems go in the soil, but it looks like it might be four separate plants. ONE plant per pot. They are competing with each other for root space, nutrients, etc.
So with not enough soil to let them grow enough roots and roots maybe crowded and pot bound, they aren't getting enough nutrients, so they are very pale and not producing very much for plants that size.
So you could start over and try again on the tomatoes, with bigger pots, more soil, etc. or you could start with something easier. A variety of herbs grow well in pots, as well as peppers (one plant per large pot), leafy greens, such as lettuce or Swiss chard. You could try a strawberry jar with strawberries, though you won't get strawberries the first year.
You didn't say where you are or what your climate is, so it's hard to make specific suggestions. But it is a challenging environment, maybe windy up that high, maybe wide temperature variations. You want to grow something that is as hardy and adaptable to your conditions as you can.
"Only when we see that we are part of the totality of the planet, not a superior part with special privileges, can we work effectively to bring about an earth restored to wholeness." Elizabeth Watson, Quaker