The canopy was to dense so I was thinking about some defoliation, but decided not to do it to prevent extra stress.
What I did, I removed weak leaves (not much though) and folded some leaves fixing with a wire to improve light penetration and air flow.
Yeah, that second plant looks really sick. Looks like it already had the problem starting from day one. Due to the white spots I would consider thrips, leaf miners or genetic defect. Does not look like powdery mildew to me. Not to dampen your mood, but I think she'll die in the next 2-3 week :(
Definitely keep both of the plants distant to each other. With damage like this, you can't know if its a virus, genetics, insects or just the dog hhaha.
But still, happy growing!
@Herikus, yes, she had that problem from the very beginning, and now I don't really know what to do. Maybe it's a good idea to put it somewhere far from others