HCA: Hermit Crab Association

Hi, new here and hoping to get some advice for my stubborn crabbies. Out of my 7, 4 refuse to wear anything but the speckled babylonia japonica shells. We're going on 3 years with them and many molts and I think I have reached the size limit of the shells. My 3 others are not as picky and have gone into turbos, but not these guys.
Any ideas? I have bought so many similarly shaped shells to try to entice them. Within the past week, everyone has come up from the latest molt (yay!), but now I start worrying about my picky ones.
Any advice would be appreciated!!
Thanks, jen
Mom of : old man, lil speckle, unicorn horn, iron man, black panther, shirley, and janet.

Apologies, I believe they are Babylon Zeylandica shells

Okay, this is unusual.

Japonica's are popular among the under one inch opening crabs. Usually at that inch mark they switch into tapestries and fluctuosis turbos. What kind of turbos are you offering?

Have you confirmed species on these 4? Some of the exotics like the oval opening more. Every so often they still get imported randomly and without fanfare into batches of crabs being sold at random stores.

The bai shells are a similar shape but run a little bigger than the japonica's, and are often a decent weight. They're white with brown splotches, and I had one at like a 2 1/2 opening once. (My biggest ate it.) Japanese Fairy Tale may also work in a pinch.

Thank you for responding!
That's what I believed too! I have both of those turbos in there and also a few black and white ones for good measure.
I haven't confirmed species, but I don't believe they are ecuadorians. I lost one a year ago because of shell stubbornness and I think that's why I am so paranoid with these guys.
Two of them are a dusty purple and the d to have orange tips, one is so dark burgundy he's almost black, and the other is a nice deep red. Last two are all over color, no tips.
Our biggest is a really bright peach with little dark freckles on his legs.
I will look into the bai shells and the Japanese fairy tales too. Thank you so much!!