Hey
@Noela, it appears as though it could be one of a few issues going on. Initially, it looked there maybe some root issues, but I grow in the same size pot and don't have issues. Do you have proper drainage at the bottom of your spacebucket? It looks as thought this is either nutrient burn or ph issues with your water. My suggestion would be to get a soil PH meter, and see what the ph of the soil is. After you ascertain what that is, and correct that, I would work towards just water for a few weeks. PM me if you have any other questions!