Especially if it skips a month as well.

Frankly it's been skipping a lot of months. Around the start of volume 3 there was a 4 month hiatus with no explanation given, and it's skipped months 2 more times since then. All of these were unannounced. During the hiatus, it was listed as returning every month and never did. It's clear there were some kind of production troubles. But that alone isn't enough for Yuri Hime to axe a manga. Chasing Spica for example has had an incredibly spotty attendance rate from the 1st volume, to the point YH almost suspended its publication; still only a temporary measure.

It's also uncommon to announce the final chapter 1 chapter in advance. And it should be noted Throw Away the Suit Together did get reprinted, which confirms it was selling above expectations, so that's confusing too. If it's because it was getting too depressing, surely YH's editors would have checked over the direction it was going, and YH isn't averse to publishing bleak manga these days either. The premise simply leads itself to ups and downs; there's no reason to think these girls wouldn't pull themselves back up and find happiness again. It's all a big mystery we'll probably never understand. This certainly isn't the way it was planned to end, not just narratively but thematically. The story's always been a reflection of the author's state of mind. I'm afraid the ending's going to be as dark as Keyyan's likely feeling.

The axe is probably due to a disagreement with her editor.
She's been skipping issues while working on another manga (which was the main cause of the long hiatus after volume 2), and last month was skipped because of her working on an anthology (which I recommend because her chapter is easily the best one).
It's obvious she has taken on these side projects because KimiShira doesn't sell enough for her to survive, the thing is that she has been doing work for companies that are not Ichinjinsha which probably irked the editorial staff and caused some conflicts between them, which led to the sudden axe of the manga.
It's especially sudden considering it was very likely planned to end with volume 4, so even if it didn't sell a lot, there was no reason to axe it.
After that, I doubt Keyyan will ever work with Ichijinsha again, and that's probably for the best because that company stinks.
It reminds me of Kuzushiro situation, where she subtly said she never wanted to be published in Yuri Hime ever again.
Honestly, it's probably a very painful situation for her, who literally quit her job to dedicate all of her energy to it, and for me, who started reading Yuri Hime for it...
I am also concerned about how it'll end because of the circumstances of its end... might have to get prepared for a very bleak conclusion...