Bloom style change on Christmas cactus
I got my Christmas cactus last year, and the blooms were the typical ones with folded back petals. This year, the buds just opened and lay flat. What causes this ?
Environmental stress can cause changes in flowers and the plant itself.
The brighter the light that your plant is exposed to, (but not direct light) will increase blooming and the actual blooms themselves.
Without seeing an image, it sounds like the plant is not receiving enough light to fully open the flowers.