I think it may be a rissoid snail. It appears to be lacking the heterostrophic shell coiling. Basically that means that the shell sprials to the apex with no change all the way to the top. Pyrams will have a 90 degree change at the very top of the shell.
A is the pyram, the other three are rissoids (which are harmless algae grazers)
I can't see the protoconch well in the pics, but all the other shell characteristics make this appear to be a Turbonilla or Amamimorula species (family Pyramidellidae, subfamily Turbonillinae). I searched for internet photos of about 10 different species that are similar, but without finding any of them. The written description or Amamimorula belonis, as well as the photo, in "Marine Mollusks in Japan" (Okutani), match your shell very well, but the singular photo I could find on the net looks significantly different. It might be an aberrant specimen, or it might be a different species (or my book could be wrong). The live-animal photos I have of Turbonilla species show the same dent in the anterior part of the foot, but some of the other animal characteristics are different. My guess is that it belongs to one of the two genera mentioned above, but could actually be one of several similar species. This family is often neglected in the popular literature, but that's not very surprising, since the same goes for most families with shells that are mostly very small.
The vast majority of rissoids (at least all that I've ever seen or read about) aren't nearly as elongate as the shell in the pics above.
That snail is one of the tough ones, since it shares shape and sculpture with species in both the Pyramidellidae and Rissoidae. You could tell for sure by examining the protoconch (the earliest whorls on the tip) to see if they curl vertically, changing to horizontally after the first few whorls (as you hold the shell with the spire up). If so, it's a pyramidellid. Dr. Shimek did an excellent writeup showing the differences.
It very well may be a rissoid. I notice that the animal appears to have a more "normal" leading edge on the foot than your first snail. If it has the normal protoconch, with the early whorls in the same plane as the later whorls, this snail may be Rissoina pura, or a closely-related species. MMJ(Okutani) says this about the species:
Size: 5mm "Shell white, but dark brown when alive due to precipitation of ferric crust. Species of this subgenus (Phosinella) having both axial and spiral sculptures on the whole surface. Sculpture fine in this species."
I balanced out some of the blue in your photo, and it appears that this shell conforms to that description, brown on the older whorls, and white on the newest ones. If it turns out to be a pyramidellid, it's a pretty good copy of this species.
Yup, the latter one is a rissoid. If it's not Rissoina pura, it's something extremely close. I reckon I'm not going to be able to improve on my guess for the skinny one. It's either A. belonis or some very similar "Turbonilla" snail (or Pyramid Snail, as the aquarists seem to call them...not sure who started that, since the ones most mollusc people call by that name are actually in the genus Pyramidella, not Turbonilla).