Collaborations during Mental Health Duress Throwaway account for obvious reasons.

I'm in the middle of a research fellowship/postdoc working with a bunch of people on various projects (in mathematics). Over the last 8 months, I have had a tumultuous relationship with my mental health that has led to many days being unable to do work. I have about four to five research collaborations that I am working on at varying stages of completion. I haven't been able to work on them as efficiently and effectively as I wish, but each is making some amount of progress to the point where no one has actively stated their discontent on the progress of said projects due to my performance.

I'm debating telling everyone what has happened over the eight months and I am unsure to what extent I need to explain my lack of engagement with each project due to personal issues. On one hand, I don't want people to think I was slacking off, but on the other hand many people will write letters for faculty positions and I don't want them thinking I cannot hack it. I hope to not mess up my academic reputation.  There's no requirement to tell anyone as I am on my own funding, so there's no "boss" that I need to tell when I take days off for mental difficulties.

What is the best way to deal with mental health issues when one is in the middle of collaborations and can't work at their standard pace? Do I tell collaborators of my current struggle or do I keep discretion as personal life should not interact with work life?
That's a pretty big "if" @YemonChoi has there.

Yes, ideally there should not be a stigma. But realistically, even if your collaborators are professional enough not to stigmatize you, are they also professional enough not to mention such a communication to others?

What has been said cannot be unsaid.

I would recommend to let sleeping dogs lie. As long as nobody has complained, you don't need to explain yourself. (Maybe people not only didn't complain, but also didn't even notice lower productivity on your part - your productivity may have been just fine for your collaborators. Consider the "impostor syndrome".) It's better to work on your issues than to explain them.

Good luck!