I'm sorry for the late response. By this time, your boys may have already been seen by your pediatrician.
You should have a low threshold to call or make an appointment to see your pediatrician if the pattern of desaturations or bradycardia has changed since discharge. As for all babies, you should continue to watch for other signs of illness including fever (or low temperature), poor feeding, decreased activity or lethargy, decreased urine or stool output, or irritability.
Your pediatrician is your best resource if you have any concerns: please call him/her if you have questions at any time about what is "normal" for your boys. Congratulations on your expanded family!