Now that's more like it

Abamectin is "translaminar", which means it is persistent and mobile within the surface of the plant, but not fully systemic. It is highly effective against mites, also effective on some insects I've used it and it works well against flat mites.

It's definitely them and and they must have been there for a while. I can see them moving under the microscope, I have spotted them on three pots with seedlings. The damage is not really noticeable with the naked eye, just a slight orange discolouration. I can't go round every pot with a microscope...

Own roots, doing well. I wonder how they'll react to being repotted?

Definitely looks like mite damage

I have quite a lot of Copiapoas, not so mature as some of yours, mostly grown from seed. I find this photo amusing. Don't assume I grow them in the dark, but in the spring I start them out with some middday shade to let them adapt after the winter.

FWIW, my mix is something like 2:2:1 JI:cat litter:grit. I find it is too light without the grit. Mixes based on the cat litter don't seem to get saturated the way a straight grit mix would, but they do stay "damp" for longer than you might expect. Perlite is the opposite, it hardly absorb...

No need for perlite if you use cat litter. Mixes with cat litter will retain more water than perlite, so adjust your mix accordingly, or your watering.

Does look like the sort of colour you get on the sunny side, not harmful, just a response to the bright light. Stress from other causes like mealies will often make a plant colour up more readily.

Pretty standard colour. This is var glabra (-ish), but the range of flower colours doesn't seem to differ.