It can, but the purple pheno still needs to be there. It’s a response to both lower light conditions and lower temps. When I grew a lot outdoors, many, but not all, plants would get varying amounts of purple in Oct-Nov, while others would get purple about midway through flowering. Others got...
Purple color is a phenotype, not all plants of that strain will show it. I’ve grown many plants with purple phenotypes, sometimes they get purple, sometimes they don’t.
3 amps is too small for 600 watts. It requires a 5 amp fuse (4.62), similarly 700 watts needs a 6 amp fuse (5+). Assuming a 120v system. If the current fuse from the manufacturer is 13 amps, I’d go with that. However, I am not an electrician, so let’s get some more input.
I always carry a pocket knife, except where prohibited. I once had to mail my favorite pocket knife to myself, forgot and couldn’t get through airport security.
It kinda cemented some thoughts I’ve had regarding P&K. I’ve always thought we overfertilized P/K, and were a little light on N, particularly in bloom/late bloom. IMHO, I think that that a lot of the plants we thought had deficiencies, actually had toxicities.
Looks like a colony of mealy bugs to me. Neem oil or insecticidal soap (if they're not in flower) should kill them, they're relatively easy to control. They suck sap and will eventually weaken the plant.
Auto's normally flower at between 3-5 weeks, sometimes up to 8 weeks (rarely). If they stall there's no time to recover. For newer growers (don't know what your experience is) I do not recommend autos until you pay your dues with photos.
Would really need a picture of the "white parasite looking stuff". Could be anything from a mildew/mold/fungus to mealy bugs. Treatments are very different.