For Spencer it was severe constipation and the development of ezcema over the majority of his body, especially bad on his face and upper torso. He also showed signs of what I now know is reflux at his feeds. Spencer's was fairly easy to diagnose as it happened once he was weaned onto formula and just before he started solids so was only really one thing that could have caused it.
Spencer was always a snotty baby as well but i'm not sure if that is a symptom or whether they can just be snotty.
If you are breastfeeding you cold try cutting diary out of your diet for 2 weeks and see if it makes a difference.
Also there is some stuff called fess little noses, it's just a saline solution that you can use to help clear out their nose, comes with a lovely little thing for sucking the boogers out too