Thanks guys.

I didn't realize it but they indeed are south facing now instead of north so they get a lot more sun, although it's the winter sun. I thought it was the temperature. Also I didn't know that at 8 months they were still so sensitive to too much light.

It really went quick (only a couple of days for the fast damage) from nice healthy vivid green little pups to white and brown disaster.  Sad but I won't give up. I had a success in sprouting them. Of 25 seeds 22 made it to this stage and were all healthy till I moved.

I have more seeds from different trichocereus species so attempt two will be taken soon.