With WordPress and Make, why are two different interfaces coming up for editing posts?

I am designing a blog using WordPress and the Make theme with some alterations I have made to the style.css file.

My site is not yet online and I have written three example posts only. The follow problem has arisen: when I log into wp-admin at my site and try to add a new post (Posts | Add New), I get a different interface from the one I got for the first two posts. This different interface is what I got when writing the third post, and it is also brought up when I try to edit the third post, but not when I try to edit either of the first two. One of the major differences is that when editing either of the first two posts the interface lets me toggle in and out of HTML whereas when editing the third I can’t.

Screenshot from “All posts”:

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As you can see, all three posts are listed. But when I start editing the second, I get this

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and when I start editing the third, I get this:

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They both seem to be using the Make theme, but they are different. How come? I would like to get the same interface – the one that comes up for the first two posts – when I write or edit any post.