Maxx, that is most likely cocci. Sulmet makes the intestines continue bleeding. You need Corid. Within five days, the cocci should be under control. If it is not, then they should be wormed. Corid is concentrated amprolium and if you can't get it at the feedstore (maybe they can order it?), then get it online. Mine comes in a 16 oz bottle and costs about $20.
You can do yogurt, you can put non fat dry milk powder in their crumble, you can use buttermilk as well to soothe the intestines. Just make oatmeal and pour it in till the oatmeal is soupy.
Is it just the chicks or adults who are pooping blood? Usually adults are immune (to what's in their home soil) unless someone brings in a form of it that wasn't formerly in your soil, either by tracking it in on your shoes or acquiring a new bird who sheds oocysts in the poop that your flock isn't used to. Corid should get it all and be easier on the intestines than a sulfa drug like Sulmet.