Those PK boosters are kinda ridiculous...even though I use them, lol.
There is no way that giving your plant extra P and K would have the effect that these products do. Plants uptake what they need and leave behind what they don't. Blasting them with P and K at the end of their cycle doesn't even really make sense - plants use way less nutrients once the buds become almost mature, than during the middle of flower.
What makes those bloom boosters/pk boosters effective is their 'unlisted' ingredients. I can almost gaurentee that products like shooting powder and dry koolbloom have some type of PGR in them. When I use these type of products too aggressively, they cause extensive fox tailing. I've actually INCREAED my flower time abusing these products, as the plants got some of that PGR and decided they weren't done flowering yet. Makes for extra weight, but IMO hasrh and ugly looking buds.
I also think that the PGRs/unlisted ingredients are what causes the harshness - which always get's blamed on the PK boost.
If your use to soil, than hydro may taste very harsh, especially if it's a strain that you are use to being grown in soil.
Of course RH has an impact on drying, that is why your drying area should be controlled, just like your grow room. If your constantly drying in a different environment, how the heck are you going to have a consistent product and fine tune your drying/curing method? The dry and cure are super crucial to the overall quality of the finished product. If your buds take less than a week to dry, your drying too quickly and I would do what ever it takes to get your drying environment dialed in.