Everyone uses Salty because of how powerful it is for both Raff and Jimmy(with Tweeter) and they use Cold on Seven for obvious reasons...
Sour, Spicy and Strong do not even come close in comparison to being as effective as Salty/Cold because in all honestly they just don't give enough of a buff to make them viable.
Sour giving us up to 30% precision damage sounds great in theory but in practice just doesn't cut it, again multiplying the damage here would work better or reworking it completely to add some other type of benefit around shooting would be better.
Strong stacks up to 60% melee damage which sounds great but even with a full melee build Pinky it barely adds any damage making it virtually useless, how about changing it so it makes Pinky bigger and her melee hits get a multiplier to the damage?
Spicy is basically a joke giving us up to +50% extra fire damage and you have to stay airborne for 10 seconds, I can pull out Hot Trigger and get +30% in a fraction of the time, once again getting it to add a multiplier to the damage would work far better.