I recently purchased a few cacti from old man cactus (one had a dead white fly in it) they were:

Echinocereus Pentalophus

Melocactus Azureas

Ferocactus Latispinas

They arrived unpotted so I put them in pots (according to the size recommended by the site) and then let them sit unwatered for about a week. I then watered them.

Since then I've noticed the Pentalophus (lady finger cactus---which came limp, which apparently is because it was in dormancy over winter?) has an opening which doesn't LOOK rotted near the base. Its just where all that dry stuff is anyways, and it's not too dry because the whole thing is as I said, limp right now.

Also, the Melocactus Azureas seems to have some wrinkling at it's base as well. It doesn't appear TOO soft, the top is fine. I'm just not sure if the wrinkling is normal.

In both cases I'm worried about rot. They both are in pots with proper areation. Broken plate piece, cheesecloth (in place of moss) and fresh clean soil atop, with gravel atop that. And the water passes strait through.

I just don't want to take them out of the pots so soon. Maybe I"m just obsessing cause I'm new. The rest of my cactus are fairing well. But I don't know what I am and am not doing right. I lost a few leafy succulents but I think I just had poor conditions.

Any help or advice on care would be great. If you think it's rot. How to detect rot i n general? Etc.