It looks like its roting

So sad, thankyou

You can still save it i went thogh it once

You have to cut the rot out cut where the rot stops

Use a (kinfe) make sure to steriliz the kinfe . Then put the health part some where until the cut drys it can take weeks.

Then re plant the part dont water water after 5-7 days then

Just have faith in it .p.s it could be rotting beacuse you over water it

I bought them like that, I thought they were unattended.

Thats ok just make sure to inspect when you buy

I will, thanks!

I wanted so badly some cacti plants that I didn't care.

Now I finally found a place where there are plenty of them to buy.

I Will try to save them though. The short one have some babies hanging around, what should I do with them? They are tiny !

Let them grow a bit don't water then cut and re plant

Like the one thats rotting

Thanks for your advice :)

No prob :)

Well, okay, before we decide that they're rotting, how do the plants feel? Hard? Soft and mushy? The second pic might just be corking imo, and i really can't tell what the issue is in the first and third pics because of the poor lighting.....I'd try and post some more pics and wait for a second opinion before you start hacking away if I were you :P

Yes, I will try more pics with better lighting, thankyou for pointing that out.

They feel hard, nothing soft or mushy.

Thanks :)

If they're not soft and mushy, it's not rot at least! c:

Good!

Here are some pics, hope it shows better.

Ana- A condtion called corking on the bottom part of your cactus and very possible sunburn on the upper part. Sometimes the burned part can cause a fungus on the cactus and it will start to discolor even more. You will have to wait and see. If it spreads I would cut the top part...right above the burned skin, set it aside for a couple of weeks to allow it to callous and then plant it in a very dry/sandy soil mixture. And, I would wait at least 4 weeks before watering it at all. After you're assured it has rooted, water it thoroughly and let the soil dry out completely (between 7-10 days) before watering it again.

In the meantime, I see from your picture little baby cactus sprouts! They are small but you can still save them in case the Mother plant does have a fungus. With a pair of tongs or if you have "cactus gloves" twist them back and forth slowly until the baby snaps off cleanly. After a week put it in soil and again, don't water until some roots have formed. You did a very admirable thing by choosing to get these plants and trying to get them to live when many others would have passed them by. I wish you all the best and let us know how things turned out : ) - NJC -

Ana
What kind of 'soil' are your plants potted in?

First one looks like a hardened pet, and second like a dense sand - I could be wrong, that's what is look to me like from your photo.
And the second plant is in a dish that I would think doesn't have any drainage holes?
Rina

Neil, thankyou very much for all the information, I will follow up your instructions :)

Rina your are right about the drainage holes, I've reading through the forum and will find a right cointeiner for it, the soil is the same that had when I bought it, its a very fine and light, its hard with no water, and the fist one it's not t sand it's like black soil but it's hard. I really need to find the right mix for them, but it's hard, cause here in Mexico they survive in whatever dirt? (Sorry about my english)

They are sold in black bags, sometimes with no dirt only this kind of little branches, sorry I don't know the name even in spanish!! Thankyou Rina :)

Ana
Don't worry, your english is very good.
Climate in Mexico is very different than what I am familiar with :-) but drainage would be important everywhere.
If you can't find better mix, I would take a kitchen sieve and sift whatever soil you have to see what remains in the sieve - I would use larger particles. Small grit would be good.
'Little branches' you mentioned - is that what plants are planted in when bought from store? - maybe it is partially composted sticks or bark?
I would think the fist plant is in peat and it got very dry and become hydrophobic - it doesn't soak any water any more. If that's the case, it is very difficult to get wet again, sometimes impossible. When you water that kind of soil, water just 'slides' around and out of pot, doesn't soak in at all.

Neil gave you very good instructions how to save the first plant (if rotting).
Rina

Ana- Absolutely follow Rina's advice with the drainage. I should have noticed that too, so I apologize for not being as observant. I wish you all the luck with your cactus : ) - Neil

Rina- you are absolutely right about that, the water just come out right trough, thakyou for pointing that out ;)

Neil- thanks so much, of course you both helped me a lot to know what's happening with my cactus, ty :)