Well! Respectfully, I disagree!

I totally understand wanting actual C&C, just as with photography, in order to get what you may be able to improve on, based on what is perceived as a "mistake."
BUT - I don't see these as having any major flaws UNLESS you were looking at a reference photo or image, or following a tutorial and your end results look way different than what was expected. In that regard, I can't say anything because I never saw a ref image - and besides, based on their own merit, they really do look fine to me.
The dandelion stem is awful. It looks like it’s a utility pole. No bend or curve at all.
One of the stems is straight up, and the other is on a diagonal. If you were trying to show your viewers some wind, you might want that curve. Otherwise, usually stems with such lightweight things as tiny dandelion seeds will pretty much go straight. I just didn't detect an unreal view.
Wisteria tree too symmetrical and too big for the paper. No light direction or shadow.
It might be a large subject for the paper size and, now that you're pointing it out, I do see where, instead of letting the line of the tree branches go straight off the page, creating an imaginary line of extension, you did crowd them, or some of them, and in a few areas the blooms look a little squished. A few areas - not all. Overall, it's no different than seeing a full-frame image with the subject going from end to end. So, visually it just didn't bother me. The colors are light and pretty, the shape of the tree is good. I agree you didn't add any blue for shadow under the tree or make any other light-directional mark - but, so what? This looks like a drawing not trying to be based in realism, and I come across paintings like this all the time that don't try to represent light source.
So - again, from casual looking I still say these are very pretty. I like your dandelions and the flowers, your sky palette is also lovely, and without comparison to any ref image, I don't have a lot of negative critique. C&C doesn't HAVE to mean negative all the time.
Anyway - hope this helps. I don't work in WC at all, and couldn't address the issues of opacity or how to back off or add more if you paid me.
