Three stories not plotted by Kirby?

"Menace From Mars" (Monsterbus p.85), "The World That Was Lost" (p.91), and "To Build a Robot" (p.96) don't read like Kirby plots to me. There are at least two hallmarks of any Kirby tale:

(1) Each is based on something that matters: either important new science or some important aspect of nature (human or otherwise).

(2) Each is full of good stuff: every page has something new and interesting, so that the stories are rewarding, even if you miss the ending.

But these three stories are different, and much weaker in my view. The Lost World and Robot stories are tired cliches: wheelchair user is a mermaid; robot hater is a robot. And they do nothing except build up to the last panel: if the last panel doesn't grab you then the whole story is a waste (breaking rule 2). The Mars story is not quite that bad, but is just annoyingly dumb in my view: not something that a scientifically curious person like Kirby could either design or enjoy. Any civilisation that had space travel would surely have a machine as powerful as an ape. And any civilisation that evolved would surely be aware of the concept of other animals. I also find the lead character's arrogance and secrecy to be taking needless risks with the human race, and the abuse of circus animals offends my modern sensibilities, but those are minor points.

Did those stories seem fresher in 1959? I can't believe this is the first time either the mermaid or robot trope were used. (Think Hans Anderson or Philip K Dick)  Was Kirby just very busy that month? Was he using inventory scripts left over from the 1957 implosion (from 85 titles, only 8 remained, leaving lots of leftover scripts and art). These stories were published May-June 1959, so presumably were produced around December 1958? To me it seems as if somebody else plotted them.

As Patrick Ford notes, "the only things we know for certain about the fantasy/science fiction/monster stories Kirby produced for Atlas from 1958-1962 are:

1. Kirby penciled them. 
2. Kirby's penciled lettering can be seen in the caption and balloon areas on every one of them (that I have seen). 
3. Stan Lee didn't sign even one of them."

So the default position is that Kirby plotted them as well: this was normal for Kirby, and most of the stories they show the hallmarks of his plots (science, new ideas on every page, etc.). However, as editor and publisher, Lee and Goodman were able to make whatever demands they wanted. These demands were always (in my view) to the detriment of the story.

This is around the time that we see the first "talking planet" image (on page 60): apparently Martin Goodman (the publisher) decided that kids liked them, so they had to appear as often as possible.  This is also around the time that Goodman noticed that monster stories sold better, so from now on there were more monsters and less sci-fi. Kirby said in interviews that he found this restrictive.

So maybe this is the point where Lee or Goodman briefly took more interest in the stories? The twist endings seem classic Lee. Jim Steranko later described how Lee suggested a plot to him, about how a planet turns out to be a child's balloon (IIRC). That was the twist ending and Lee expected Steranko to turn it into a full story. (Steranko found it a poor cliche and ignored the idea.) I wonder if Lee made similar suggestions here? If so, then I'm glad he didn't do it often. Kirby is a much better writer and his plots are usually so much better than that.