All pages blank except home page

I had to disable Nextcellent to get my client’s site working today. The error log shows:

[17-Dec-2016 17:58:12 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/nextcellent-gallery-nextgen-legacy/lib/image.php:469) in /wp-includes/pluggable.php on line 1179
[17-Dec-2016 17:52:33 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/nextcellent-gallery-nextgen-legacy/lib/image.php:469) in /wp-login.php on line 394
[17-Dec-2016 17:52:33 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/nextcellent-gallery-nextgen-legacy/lib/image.php:469) in /wp-login.php on line 407
[17-Dec-2016 17:47:27 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/nextcellent-gallery-nextgen-legacy/lib/image.php:469) in /wp-content/plugins/wptouch/core/class-wptouch-pro.php on line 355
[17-Dec-2016 17:52:31 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/nextcellent-gallery-nextgen-legacy/lib/image.php:469) in /wp-includes/IXR/class-IXR-server.php on line 149
[17-Dec-2016 17:52:31 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/nextcellent-gallery-nextgen-legacy/lib/image.php:469) in /wp-includes/IXR/class-IXR-server.php on line 151
[17-Dec-2016 17:52:31 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/nextcellent-gallery-nextgen-legacy/lib/image.php:469) in /wp-includes/IXR/class-IXR-server.php on line 154