I have had both success and failure with cuttings that have peduncles. Some species will continue to bloom, even while rooting; other species are divas and will drop their peduncles if cut. Many species will keep their peduncles, but you may not see blooms until the new cutting has formed a well-established root system, and has put out new growth.

You WILL want to make sure any cuttings you take have foliage on them, as well.

As far as the yellowing is concerned, it may or may not be a nutrient deficiency. I always check root systems, if my plants start to yellow (I also fertilize on schedule, so it is less likely that my plants are suffering from a nutrient deficiency).

If needed, I will re-start a plant with root rot or failing root system. Or, if the root system is fine, but my potting mix has become an issue (old, decomposing) I re-pot with fresh mix.

In any case, it's never a bad idea to take cuttings, if you suspect an issue!