Side view of one cacti.

different species, different problem?

Th mix is to Heavy. You need to clean off the soil from the roots the best you can..peat tends to turn into a hard rock, then you need to pot them up with either a gritty mix or a combo of %50 Cacti and succulent (istrain the Heavy meterial outta it) then ad %50 perlite for BETTER drainage - water only when soil is completely dry thru out, put your finger into the medium if it's damp don't water if its dry give it a drink! And slowly introduce to full Sun over a few days.

@KittieKat! Thank you so much! Only one is left now, the other finally packed it in.

I seem to be killing off all types of plant life these days, I shouldn't be trusted!

I'll follow your instructions and hopefully the prickly fella will live! Thanks again.

Keep in mind also that these are plants accustomed to harsh climates where they don't get more than a few inches of rain per year(typically). And usually you will see signs of them needing for water such as wrinkling or changing to a yellow color(although this can indicate other things as well. Sometimes it indicates nothing but age as in a cactus that develop a yellow/brown "stem" at the bottom also called a caudex). I would recommend rock, pumice, granite over perlite though. But there is no harm having perlite in there as well.

Good point, actually several good points. And food for thought for me, I need to be a better carer of cacti. I always have the best intentions, but inevitably I kill them. Likely because I've presumed they're simple to care for, and the simple doesn't include over/under watering.

I've had to let go one of the cacti, the other is barely hanging on. I'mnot sure what to do as it seems salvageable. But it's buddies (who he's attached to I think) are all dead. I wouldn't want to damage it any further by reporting it, If there's a better and safer alternative.

Any thoughts? All welcome.