A star consumes quite a lot of hydrogen in its life, and is pretty much "vacuuming" everything in its vicinity. After it dies (eventually by supernova which will spread all its composition over light ...
There are various modes of Cepheids like single modes: fundamental (F), first overtone (1O), and likewise. And then we have double modes: F/1O, 1O/2O etc. triple modes: 1O/2O/3O etc. ...