Noticings of Early May

I've been eying a few new discoveries in the tank.  Some have been for weeks, others only a couple of days.

Not sure what this is, but to the eye it looks like a seedling.  Here with magnification, I'm back to being stumped.

Not sure what these two things are, either.  A good picture of the "Feather-Mounds" is in the first image of the "seedling" directly to the left.