Cannot join a web server in DMZ to a DC in the DMZ - Instead, I had to open network firewall ports to allow the web server to communicate with the DC on the inside.

I cannot join a web server in the DMZ to a DC in the DMZ on the same Ethernet switch.  Instead, I had to open ASA firewall ports to allow the web server to communicate with the DC on the inside.  I have "AD Sites and Services" configured for both IP subnets and corresponding DCs.  I also now see servers on the inside attempting to communicate with the DC in the DMZ.