I've started tomato, peppers, and cucumber seeds indoors all come up and get about 1"-1.5" high then seem to wilt. I been pulling the wilted plants out but the other seedlings seem to follow suit. I planted them in peat cups. styrofoam, and plastic starter containers. I have them setting by a window and I turm them when they start to lean toward the light. I water them good about two to three times/wk.
You may be referring to damping off, a fungal disease. The soil media may be poorly drained and kept too wet. They need holes for drainage.
Use soil less potting media for growing transplants. Don't over-water seedlings grown indoors or in a greenhouse or cold frame. Allow the top of the growing mix to dry slightly before watering. Plant seeds and transplants in loose, well-drained soil. Infected plants should be pulled up immediately, indoors or out in the garden, and composted. See more information on damping off indoors and in the gardenhttp://extension.umd.edu/growit/poor-germination-vegetable-seedlings-and-transplants
and tips on Seed Starting Indoors http://extension.umd.edu/growit/food-gardening-101/starting-vegetable-seeds-indoors
After germination, seedlings require strong light. Place them 1-2” beneath a fluorescent fixture for 14 to16 hours a day.