Rogue SPAC SWAPPING

When I change specs on my Rogue, my poisons are either supposed to drop off or not drop off. Because one of them always falls off and the other one does not.

Crippling poison does NOT fall off when changing specs
Instant poison DOES fall off when changing specs

Not sure how blizzard wants this to work. But only 1/2 working, isn’t right.

regards,