If you view an album that's listed on your profile page on a mobile device, the default setting causes that album to be shown using jAlbum's own mobile interface. In other words, when viewed on a phone, it's not being shown with the Turtle skin at all.
You can force the album to be shown with its actual skin by going to your profile page, hovering on the thumbnail for that album, choosing Edit album, and then checking the box to disable the automatic mobile version.
However, Turtle is not a fully-responsive skin, unlike Tiger, it's new incaration, so it's not going to work well on a smartphone.
If you mostly like Turtle, but want your albums to be fully responsive on mobiles, then the answer is simple: Tiger.
Edit: There actually aren't all that many skins that are fully responsive. Just head for the skins page - https://jalbum.net/en/skins/new - and check the Responsive layout box.
There are only 18, and that really overstates it. Two of the skins, MinimalFX and MinimalWeb, are just variations on Minimal, more as coding demonstrations than anything else. A few of them are really just skeletons of skins, done by long-gone jAlbum interns, with few options and no meaningful support.