Yeah, sorry I didn't see that before. To the best of my awareness you need a separate ALTER TABLE statement for each column.

I vaguely recall trying different combinations of syntax before, to avoid separate ALTER TABLE statements, and I was never able to get it work. I think at one point Naomi and I were talking about this, and I don't remember if either of us ever came up with a solution (other than separate ALTER TABLE statements)

I think you can do multiple ADD statements with just one ALTER TABLE, but I don't think you can modify multiple columns with just one ALTER TABLE.