I agree both twins need to be seen by the pediatrician. Snoring in an infant or child is never normal and definitely needs to be addressed. He probably should have a chest X-ray to rule out a pneumonia.
On twin #2, the medication he was given - did it contain codeine or anything along that lines? If so, that could be adding to his already present constipation problems. Bright blood on the stool is usually caused by something like hemorrhoids or like mammo said, tearing while straining. It's when the blood is dark and mixed IN the stool that you really need to be concerned (not that you shouldn't worry with any type of bleeding from the rectum).
How are the twins drinking? Taking in additional fluids could help both of them - twin #1 it will help thin out the mucous to make it easier to expel and twin #2, it could help with the constipation. I would suggest limiting their milk intake, as dairy products can not only add to a mucous problem, but they sometimes can be constipating. I would offer something like pedialyte/diluted gatorade or apple juice (this may help with twin #2's constipation also). Even letting them suck on an ice pop/popsicle would help get extra fluid into them.
I hope they feel better real soon!
Twin #1 needs to see the doctor about the breathing problem. Twin #2 has constipation and it sounds like when he does go it is tearing his anus, which causes bleeding. He is not going so much now, because he knows when he goes it hurts, and he is trying to hold it, but some gets out. He too needs to see the pediatrician about the constipation issues.