You're over watering by watering too often and it's causing damp off.
You could get away with watering that pot once per week, twice at the very most. In this case too, i'd be giving nutrient fortnightly, rather than weekly.
Love the creativeness with the matchsticks!

A small stake would serve you better I think. A skewer and loose twist tie would be suffice.
You need to let that top soil dry, that's what's causing your dampoff.
An inch or so of straw or similar mulch would be beneficial too. It'll help keep the soil evenly moist and will allow you to water less often, whilst also not letting the top soil go too dry, too soon.
Leave a small amount of space between the base of your plant and the straw, so the plant can breath and you'll be golden.
P.S. Stretchy seedlings are more susceptible to dampoff too. So as mentioned above, you might need more light.
Plant's very young too, so go really easy on the nutrient. Over feeding plants is very easy to do. Less is nearly always more.