When building a niche website, should I focus on one category only?

I noticed that my competitors focus only on one category/sub-topic, while I cover four categories/sub-topics on my blog. The categories are related to each other, though. Does this put me at a disadvantage? Will it take longer for me to rank compared to my competitors because each category needs its own topical authority? How does this work? Example: let's say my blog covers **strength training, nutrition, yoga, and mental health**, while my competitors focus on **just one** \- e.g. only yoga, only nutrition, or only strength training. Does focusing on multiple categories *dilute my topical authority* compared to them? Would it be better to narrow my focus to one category, or is it still possible to build authority across all four topics over time?