How does that weapons swapping actually work with certain passives?

Situation: i have two croosbows, one for bolts(A), other for grenades(B).
On skill tree A i had speced into damage against low life, on skill tree B i have grenade area of effect, damage, and repeating explosions.
Question: If i shot a bunch of grenades with set B, then swap back to set A, do does shot grenades regain abilities from tree B, or they instantly lose it? And if its the latter, is it a permanent loss, or until i switch back to set B?
Also, does those shot grenades gain damage on low life bonuses when i switch to set A? That would be kinda absurd, but i'm literally guessing here.