Subscriber number dropped overnight!

[Alex L]

Help! I've been slowly building subscribers, had reached 51 after 9
blog posts (with some up and down variation here and there) when this
morning I discovered I'd gone overnight from 51 subscribers to 22! I
just don't believe 29 people abruptly un-subscribed. Can someone help
me understand what may have happened and how to correct it?

My blog url is http://happinessinthisworld.com
I am using wordpress.com

Also, a second question: I understand there's a 512K limit on feed
size. Does that mean the total number of posts must not exceed that
limit or any one post must not exceed that limit?

Thanks for a speedy reply!

Alex