I bought a Kalanchoe Fedtschenkoi (Marginata I think) last week and it has been doing great. But the stem condition is not the best ever since I bought it. I picked this one cause the others look more terrible.

My issue is that the stem looks rotten, eventhough it's not mushy when I touched it. Here's a closer look:

The main stem is my biggest concern. It also has a broken stem in the middle which also has this sort of brown-ish 'dry' color. I can't take a clear photo of it cause it's covered by the leaves:

There has been a lot of tiny insects (I don't know the name of it) which has a pink body with a lot of tiny white legs. They're really tiny like only 1 mm long. The insects have been crowding the broken stem but I've cleaned them all, hopefully they won't return.

I think the seller doesn't really care about the succulents' quality but I've been wanting this Kalanchoe for a while. What do you think happened to the stem? Especially on the 'rotten' part. And what can I do to help it? Much thanks!