I planted 2 seeds about 3 weeks ago and the plant seemed to grow pretty much okay then the leaves started to turn kinda Brown and now it stopped completely it's growth. They almost have full sun all day, maybe it's too much?
It's hard to see, but that looks like mould. I also notice that the out-of-focus potting medium looks very dark, which is not in itself an issue, but most composts tend to appear darker when wet.
So my first thought is - how much are you watering these plants? Chilli peppers are from hot, and often fairly dry climates, and are not fond of an abundance of water. These are young to go very long without water, but being on the cusp of wilting before being given more would be absolutely fine for these. They also look to be in a planter. Do the pots have drainage holes in the bottom? If not, you must be very careful not to have any water pooling in the bottom of the pot - as you can't see this, the only way to judge this is by common sense and erring on the side of too dry.