Z.L.
They may really be hungry and not just having a hard time going back to sleep. Everyone has different philosophies but my pediatrician recommended feeding on demand still at this age. However, you may have a different recommendation from your dr. My daughter was fed on demand and eliminated night feedings on her own until she slept through the night around 5 months. Every baby is different and your needs may be different if you are back at work and need a good night's sleep (I am a SAHM and could nap during the day to catch up). Neurologically babies are too young to be allowed to cry it out until they hit around the 6 month marker (which it doesn't seem you are doing) so you may have to help them with getting back to sleep a little longer.
Sorry this may not be the answer you were hoping for. Good luck.