Originally I would have agreed it was a bleached crispa, but the foot pic being redish color would make me suspect bleached BTA, but bleached either way.
Bleaching is not a chemical process done by collector, it happens during shipping quite often, poor light and conditions.
Small feedings of mysis will help regain health.
A crispa's base is yellowish, an LTA has spotted veracue, the redish is typical of BTA