OP, you're in a tough situation and your concern is legitimate. Unfortunately, I think a lot of staff education must happen in your setting. Typically, the residents in your SNF has had at least a 3-day acute care hospital stay where hopefully the medication list for each particular resident were fine tuned and reviewed by a provider in the hospital prior to discharge so that there shouldn't be any reason to hold the medications because they are prescribed at maintenance dosing just like what would happen if the resident was at home recuperating.
That said, your patients are in a nurse-monitored setting in terms of vital signs and clinical assessments so it is reasonable for a nurse to question whether to give a medication or not based on assessment findings. That, however, should be communicated to a provider not because the nurse has no independent judgement skill but because the legal scope for acting on whether meds must continue rests on providers not nurses. You're right to say that not all "BP lowering meds" are purely used for BP control. That is where speaking to the provider will help to clarify indications.
For medication safety and to advance the quality of care of our elderly in SNF's, I'd say this is a serious issue in your institution and you might want to discuss it with whoever is in charge of staff development or even the DON.