Mycophile, listen. I can give U probability with more then 75% accuracy what is wrong with this oldie. How old is he? 2008-1966=42 years!! :!:

Very nice! I presume that cacti is straight from Sonora desert? :nod:
Made from button? This "little" clone bro? I can see many wounds on him,
couple harvestings came from U little guy? Aren't they? :yawinkle: Just by looking on your back and counting number of heads I can tell that U were harvested minimally 3 times. :question: Is this true?
Back to problem.
If this cacti hasn't seen new soil for more then 3 years period he needs it momentarily!!! :axe: :!:
Before any doings on Peyote replanting U need to have soil out water for at least one week!!!! :!: If it isn't dry that long or if U have maybe water it today(bad luck my friend) place it on radiator or somewhere near NORMAL heat. Nothing above 35C°!! And try to evaporate as much water is possible!
Next thing what U need to do is right soil mixture. There exists shit load of soils for each plant itself(wonders) but combining can make wonders into miracles! :goodman:
U need "cacti" soil 60%, 20% of fine evergreen black soil or normal plant soil, 15-20% of clay (look round your hood, dense and sticky soil with brown shit color is what U want), rest 5% could be earthworm residue (little piles of sticky soil) mixed with clay but that isn't so important. (maybe can do more damage then good cause those little piles are one of the most fertile soils on Earth with high mineral levels within!!!!)
Use some fertilizer, watch how U use it! How much! Use less then more. Use only 60% of recommended cause new soil will give U what U need.
Fertilizer needs to be combined with those two minerals!!(N&P) They will help your Peyote to defend himself.
But watch it!!
If U are unexperienced cacti grower use only 50-60% of mine recommended dose for Peyote CACTI!!!
ONLY 25% from 50-60% Do not ever look other plants and how much bottle say and how much N and P fertilizer they need. I fry some cause of that. Maybe U will need to buy two of them cause U need same number of minerals. Also watch how U mix that closely!
(N) nitrogen - encourages good top growth.
(P) phosphorus (phosphate) - encourages good root growth
I am writing this post some time and forgotten has this cacti been on sun this year?!?
NEXT TIP IS FOR EVERYONE!!!! REMOVE SMALL BROWN MARBLES FROM CACTI!!!!!! THEY ARE DISEASE CARRIERS!! MOLDS, HIGH MOIST ON NIGHT TIME, FUNGI, NOT TO MENTION SUBSTANCES FROM THEY ARE MADE!! DENSE CONCENTRATION OF "TOXIC" MINERALS!! REMOVE THEM AT ONCE!! THEY LEAVE DISTINGUISH RUST COLOR ON CACTI LIKE ONE ON YOUR PEYOTE!! CUT OF AND PEAL OF "RUSTY" PARTS FROM CACTI AND CACTI HEADS.
RESPOND QUICK AS U CAN AND TELL ME WHAT IS HAPPENING WITH THOSE "MARBLES" AND RUSTY SKIN.
SEND MORE PHOTOS, OF SOIL, OF DETAILED HEADS, THINK LITTLE, NEED YOUR HELP JUST LIKE U NEED MINE.
PEACE
LIGHT
BLESS
LOVE