I recently moved all 50 of my 5 week old chicks into a coop which was quite stressful and they are dropping and dying like flies! There seems to be a bloody mucus that they are discharging... they are all bent over, not eating, and listless. Every 5 hours or so.. 2 or 3 die! Is it possible my whole coop is contageous? Previously I had 30 hens in that coop, and granted, it was quite unsanitary, but I removed all the droppings and raked it before moving the chicks in there. Help!

Sounds like maybe a bacteria reproduced in the coop with the previous hens that may have survived in the coop. Did you try disinfecting? Have you tried moving the chicks to a different enclosure? What is the coop made of (some materials will encourage bacteria more than others, especially if weather is warm or humid). Sorry I can't offer more info than moral support but that's the limit of my sick chick knowledge. Good luck with your chicks !

You need to get the remaining chicks out of that coop.
Start them on terramiacin or other meds.
You need to thoroughly disinfect the coop; to include washing inside and out with a bleach solution.
Let the coop air out until completely dry, and it doesn't smell like bleach anymore.
Don't reintroduce the chicks to the coop until they are well again.
Make sure they have plenty of litter (pine shavings).
It would also be a good idea to put bio stress pack in their water, and bonemeal in their feed.

If the bloody mucus is coming out the back, it is likely to be coccidiosis at their age. Where is it coming from? Describe all their symptoms. Are they sneezing? Eyes watery? Are they eating?
It sounds like you should begin by getting them out of that building. Is the floor dirt? To sanitize the building, mix bleach with water at a rate of 1:10, and wet every surface inside the building with it, then close up the building. Wait 3-4 hours, then open up the building and allow to air dry. Repeat. Watch out for fumes as you do this. The chlorine in the bleach will get you if you're not careful.
This is a good illustration of why young birds and old birds should not be mixed. Write back and we will help as much as we can.