If i had to guess from 4000 miles away
i would say that the mother had mites and or thrips,they dipped the plant and got rid of them all but the mites and thrips had already infected the plants stems and now all though the offenders are gone the diseases that they spread and the damage they do have spread to the rest of your crop.
Apparently the germs spread by thrips cannot be gotten rid of.
I wouldn't buy clones from that place ever again as they obviously either haven't a clue or are ripping people of for money.
Seeing as the plants have been dipped to get rid of whatever bugs there were i expect they just ripping people of and trying to get some cash back on their ruined plants.
We know that there were some kind of bugs infecting the leafs because of the spots so we can assume that they are using bad clones either out of foolishness or profit greed