Im a little confused how you have gone from nutes to bugs in this thread.
You will need veg nutes, the soil lasts about 2 weeks then def appear. Use hydro veg nutes in the soil starting 1/4 strength working up to full str.
Salt/nute burn due to letting the soil dry too much too often. Dont let the pots dry out it stresses the plant.
Its very hard to over water a healthy vigorous plant.
The medium is no good for growing dope indoor. Try a better medium next grow with 30% perlite.
Reduce watering , dont feed, dont re pot and hope they bounce back.
Ok i can see the new pics and its nute/salt burn. Try a better medium next time and dont let the pots dry too much this causes salt burn as roots are in the dry salty medium with no water. Nothing you can do now just remember in future. Its very hard to overwater a healthy vigorous plant but...
The medium is too hot for seedlings. When you put them under the big light they stress because they're not healthy. Change to a mix like coco , perlite and peat and then you control the feeding not the medium. The reason the soil wont dry is because of the health of the plant, sick plants dont...