I'n not sure I see the blemish you mentioned. Maybe the lighter colored area near left top and center top? I can almost see a leaf shape there. Probably if you wipe it back a little like you said, it could easily become another leaf.
I did read your "rough time in class", and had to laugh. Some senior ladies do feel very possessive of things they don't possess. I'm a senior lady, but haven't quite reached that stage.
As everything is a learning experience... will persevere... Maybe I can rub that part back and stick another leaf there
I sometimes worry that I should not start over so much, but then an artist friend, (with a degree in art and I'm mostly self-taught) told me to think of starting over as a learning experience. I felt better about it then. But it does run the price of paper up. I have started using just mostly colors that are transparent non-staining and they can be wiped back and lifted up pretty well. Burnt Sienna, Cobalt Blue, and Quinacrodone Red are colors that lift easily to make possible some corrections. Sometimes I just turn the paper to the other side if it is something I am not planning on selling. I do like Arches paper, 140 lb. and 300 lb.
Your sketch of the magnolia looks very authentic. I like that you have one fully opened and the other half open. Magnolia is my state flower and I have 2 of the trees in my yard, both a different species.
Looking forward to the next installment.