If I understand this page right, https://lemm.ee will never show the top post of the day from https://lemmy.blahaj.zone/, https://discuss.tchncs.de/, or https://feddit.uk/.
The top posts from all of those instances will have a chance to appear on your front page of lemm.ee, as long as at least one lemm.ee user has previously subscribed to the community those top posts are posted on!
If you put your front page on "subscribed", then you will see posts from all communities you are subscribed to, regardless of whether these communities are lemmy.ml, feddit.uk or any other instance.
If you put your front page on "all", you will see posts from ALL communities that have at least one subscriber on lemm.ee (again, regardless of what instance these communities are housed on).
So to be clear, you have nothing to worry about! 😃
Let me know if any of this doesn't make sense, I'm happy to explain further.