Is it rot?

[Theo]

One of my small sprout suddenly look weird and is soft and "wrinkly", is it rot? i left a plastic hood on it for some days, but maybe i forgot to get some fresh air in there

[Kisal]

You have probably diagnosed the problem correctly. Cacti don't like too much moist air around them. The need good air circulation.

I would leave the little seedling alone, to see what it does on its own. If the rot is significant, the plant will die. If it's just barely beginning, the dry air might allow the plant to recover.

[Theo]

Kisal, you are, once again, my hero !
I have around 14 seedlings at that size in the container, but it's the only one that had it. The hood is removed, and i don't think it going back on if i risk loosing one of my little guys
(ps. it's hard waiting for them to grow bigger!! so slooow)

[Kisal]

I know! They're such pokey little things when you want them to get bigger! Then, when they are big and filling all the space you have available for them, they seem to continually sprout up like rockets and need larger containers!