Bad practices won't change DNA or gene expression. You need long term threatening environmental pressures to turn genes on and off, generally. Like heat to create the expression of heat shock proteins. Likely something similar with drought, etc. but these are temporary expressions.
This genetic drift described lasts, and I'm not sure is reversible. My inclination is that the lack of UV over generations of a clone might turn a gene on or off. Sometimes. On some strains. Central to this is the testimony that the negative traits are not seen on the same strain raised outside. That's very telling
