Night Light only affects a single monitor now

[Nathaniel W. Turner]

The Display settings have a "Night Light" option which allows reducing blue light at night.
In Ubuntu 17.10, this worked great, and the setting took effect on all 3 of my monitors.
In Bionic, only the 1st monitor is affected; the other 2 remain at the default color temperature.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xorg 1:7.7+19ubuntu5
ProcVersionSignature: Ubuntu 4.15.0-10.11-generic 4.15.3
Uname: Linux 4.15.0-10-generic x86_64
.tmp.unity_support_test.0:

ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: GNOME
Date: Wed Mar 7 17:51:02 2018
DistUpgraded: 2018-03-07 12:52:16,474 DEBUG Running PostInstallScript: './xorg_fix_proprietary.py'
DistroCodename: bionic
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, including running git bisection searches
GraphicsCard:
 Advanced Micro Devices, Inc. [AMD/ATI] Tahiti XT [Radeon HD 7970/8970 OEM / R9 280X] [1002:6798] (prog-if 00 [VGA controller])
   Subsystem: XFX Pine Group Inc. Double D HD 7970 Black Edition [1682:3211]
InstallationDate: Installed on 2014-08-21 (1294 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
MachineType: To be filled by O.E.M. To be filled by O.E.M.
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-10-generic root=UUID=98fea0b5-8fa6-4625-bae5-b85a70783a13 ro quiet splash nomdmonddf nomdmonisw nomdmonddf nomdmonisw nomdmonddf nomdmonisw vt.handoff=1
SourcePackage: xorg
Symptom: display
UpgradeStatus: Upgraded to bionic on 2018-03-07 (0 days ago)
dmi.bios.date: 04/18/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 1208
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: SABERTOOTH 990FX
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1208:bd04/18/2012:svnTobefilledbyO.E.M.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnASUSTeKCOMPUTERINC.:rnSABERTOOTH990FX:rvrRev1.xx:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.family: To be filled by O.E.M.
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: To be filled by O.E.M.
version.compiz: compiz 1:0.9.13.1+18.04.20180302-0ubuntu1
version.libdrm2: libdrm2 2.4.90-1
version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.0~rc4-1ubuntu3
version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.0~rc4-1ubuntu3
version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.5-1ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.10.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2
xserver.bootTime: Sat Oct 7 12:18:20 2017
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.19.3-1ubuntu1.1
xserver.video_driver: radeon

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.