Thanks for your reply dg, much appreciated.
They are in a small room with one window out of direct light.
The top two photos are examples of the worser yellowing and softening on the base.
I rearranged them yesterday in the trays and 8 of them have spots at the base which really look like rot (or in some cases tissue damage on the top like small holes in which you can see the fresh green flesh) . I separated those from the rest.
After reading almost the whole night about this problem the general consensus on other the cacti forums seemed to be that they are under watered. Which could very well be the case as the soil was cork dry and I didn't gave them water for 2-3 weeks.
Temperatures are like 17-20 degrees right know. So I decided to water 1/3 of them to see if there will be any difference. This morning 3 of them showed small bright pink fresh flower knobs
.
The one that had that rot spot on the photo I decided to dry. The button was 4.1 cm in diameter and about 1.5 cm in height. It's dry weight was 8.61 grams and it's dried weight was 0.59 gram so the wet/dry ratio is around 7%. That 2-3 percent more than my experience with trichos.
The root of that one I cleaned and replanted. It had a purple like purple spot which I cutted out with a sharp heated knife.
About the grafting, I really want to practice with that but I only have big diameter san pedro's and torches, which probably are way to big for grafting a peyote onto. I was thinking to cut one of my new pedros and leave 10 cm at the base to put one of the biggest lophs or one of my clusters on. In all topics I found on the net about grafting larger lophs on pedro they all seem to match in diameter. Most topics are about seedlings on periskiopsis.
Do you happen to know a good alternative to miticides? I read about someone on a cactus forum that he used cinnamon powder. Some of my clusters could have those mites as they have some of the small pups covered in a rusty color and there were some kind of thin spider webs on some of them which I removed. They are in a separate room away from the single head lophs.