Thanks all! I'm soaking all the answers in.

I have a copy of the test and will have to grab it. The rubric didn't test for creativity in writing at all. It was all mechanics. My oldest I actually thought was a very good writer, but not according to this test.

I do want my kids to be decent writers and spellers. I feel it's important. So that is definitely something I want to look into.
We do see a pediatric opthamologist, so I will bring Katie Grace's writing sample and ask her to take a look. To be honest, I think it probably has more to do with the fact that we do Waldorf-inspired homeschooling and do a lot of writing in blank, unlined main lesson books, so she's just not used to writing on lines. Still, it's a skill she needs to learn.