Help me

The leaves are like this because you had it in a humidity dome and also from having too much light. The humidity dome has suffocated this plant as it does not let the plant transpire/"sweat", meaning its stomata/pores get clogged and there is no way for the plant to get rid of waste products. Plants need good air exchange to grow properly. Cannabis seedling really do not need "humidity domes" of any sort and they do NEED sleep, so go to 18/6, which is optimum and leave it uncovered and in a few days the new growth that appears will be normal. These damaged leaves should recover too with a bit of luck. Even if they don't, it will not really affect final results. A few days without sleep, without fresh air and with excessively high humidity are the reasons your plant now looks like this, it has basically been "cooked" inside a humidity dome full of stale air. The soft and weak stem is also the result of the humidity dome experience. Wait for it to recover and it is putting on new growth before doing anything like transplanting it or feeding it with something. Right now it is in a fragile state and the last thing you want to do is stress it with changing pots or throw it a T-Bone steak (root juice). The only time humidity domes are needed is for cuttings/clones, as they are waiting for roots to form, otherwise open air is essential for healthy seedling development and air movement is also essential for strong stems. Hope this helps, Organoman.