Why is my follower per day dropping?

I still post decent content and get pretty good engagement/comments, but no one seems to follow me. I follow people in my niche, especially the one's that actually comment on multiple pictures etc but they don't seem to follow me back. I even spam like their stuff.

Anyone know what else I can do?

there's something going on, like a silent purge or sth. many accounts say they're losing followers lately..

Perhaps your referrer sites are themselves losing traffic.