How do I know if my Dad isn't being taken care of in the care home they way he should be?

He cannot walk and forgets short term things lately my instinct s when I go to visit him things don't feel right his bottom won't heal cause there not changing him overnight bleeding sores and days he's been arguing with owner house manager she's been doing this for years so she should know how to handle dementia without confrontation how should I approach this matter without making it worse for my dad I thought he was in a good place most of the girls there do a good job