Generally speaking, when batch sparging:
-Additions to mash (salts, acids)
-Additions to sparge (maybe acid or maybe nothing)
-Additions to boil kettle (salts)
Generally speaking, when fly sparging:
-Additions to mash (salts, acids)
-Additions to sparge (acids)
-Additions to boil kettle (salts)
"Sparge" salt additions are generally better served directly in the BK. Sparge acid additions are mostly only needed in fly sparging since you run a much higher risk of pH raising than you do when batch sparging, thus the reason why you may want to simply forgo any acid additions to the sparge when batch sparging.