5:44 AM, Saturday June 19th 2021
Great progress!
I am using a different medium than you, so my critique might no be the best.
Your improvement throughout the lesson is noticeable. What I can see immediately is that some of your drawings are more organized in terms of construction than others. But that is normal and part of the learning process, just remember to add only what you need to, and try not to go overboard.
As uncomfortable said, be gentle with the line weight. If you add more line weight than necessary it becomes less effective and results in a noisy drawing. e.g. Your last plant drawing has considerable amount of line thickness overall, which forced you to make even thicker lines in some of the leaves to push them forward. This is why adding more line weight to it didn't help.
Since you are using a traditional medium, you should go easy on the line weight at first. This would be the best approach since you can always add more thickness if you need it later. However, if you try to do it the other way around, you wont be able reduce the thickness, and you will be forced to add even more line weight, just as I pointed out before.
Other than that, some of your branches look like they were chicken scratched. I assume this happened because you tried to make the branch in sections, which is fine. However, it is essential that you plan ahead before putting down the line. Use the ghosting method so that you are more likely to hit the mark than not.
Finally, a personal opinion. You mentioned the following "For the last plant I tried putting a black background in the middle like Uncomfortable did". It's fine to draw along and sometimes copy the technique of others through observation. However, you should take time to identify your weakest areas and reinforce them with additional practice and material, so that you truly understand what is going on, and what you are doing.
My point is, if you are having trouble casting shadows or anything else that might not be covered in these lessons, try to find other sources. This is exactly what I did with perspective since it was bugging me even after 250 box challenge. I'm still a beginner, but I ended up with a much better understanding of it after learning not just from uncomfortable, but from other sources like Marshall Vandruff as well. As long as you get to understand what you are doing, and you get your questions answered, why not?
That might have been a hot take, or not.
Anyways, you seem to be making lots of progress, keep it up!