For some of your plant constructions you made most of the lines very heavy and dark. This does help make the actual flower stand out from the scaffolding (sketch marks in construction) but it can go against the depth of the drawing overall. If you only darken a short part of some lines this makes it so you'll have to do less work and it would help with the depth of the drawing. What I mean by that is: in some lessons, we are recommended to darken lines regionally. If something is in front of something else and the lines intersect, then you can darken the line of the object in front of the other. However, you only need to darken it in the region where they intersect, instead of darkening the whole object. This means you won't have to darken every line you put down previously and it can help establish which lines are in front and which are in the back.