I'm new in gardening and these stuff. So I planted some ipomoea seeds some time ago and at first they were growing nice and fast but suddenly they started to get wilted yellow and these brown spots appeared on them. I water them daily (1 cup of water approximately). I use Perlite, Garden soil and Compost (Vermicompost to be exact) as my soil mix for their pot. they get 6 to 8 hours of full sun every day. So where did I make a mistake? Is there anything that I'm missing?
The problem is you are watering them every day. You should only water plants when they need watering, not on any kind of schedule. As a general rule, you should water plants when the top inch of soil is dry to the touch. You have to be extra careful with seedlings because excess moisture can often cause damping off disease. Damping off disease is a fungus that spreads on the surface of the soil and cuts down seedlings (they will look like the stems have broken).
A good way to try to prevent damping off is to brew some chamomile tea. When it has cooled to room temperature, put it in a spray bottle and spray the surface of the soil. It is okay if you get the tea sprayed on the seedlings, chamomile tea is very gentle and safe on most seedlings.