I pay close attention to the critiques the members of my online group do for me, but I also read most of the ones they do for others. It's almost equivalent to taking a class on writing. I've learned a lot reading what others have to say.
One of the things I've noticed that is said fairly often is that there are two stories in a submission that should concentrate on only one. I've had it said about a few of my own submissions, and it came up again recently in a story someone submitted as a possible Chicken Soup for preteens story.
It happens when we write too much of an introduction or give too much backstory. In the one I read yesterday, the author had a lot of intro material that was interesting and was most likely done to set the scene for the real story which began more than halfway through the piece. It's where the action began and where my interest heightened. I'm sure she felt all the intro part was necessary to the telling of the active part. And a lot of the information in it was most definitely pertinent.
I would rather she began with the action part of the story and weave in the needed background information. For one thing, it is going to grab the reader's attention sooner. Or she could use the information in the earlier part to write a separate story, turning one submission into two submissions.
As I said, I've done this myself more than once and not even realized it until a critter pointed it out in her critique. When I concentrated on one part and made it into one story, guess what happened? The story became much stronger. I've learned that the answer to One or Two? is almost always One.