You may want to check your FPM Pool Configuration. You can also set php.ini settings there which in my opinion is a better place when using FPM.
You'll find something like this at the end of your FPM Pool Configuration:
; Additional php.ini defines, specific to this pool of workers. These settings
; overwrite the values previously defined in the php.ini. The directives are the
; same as the PHP SAPI:
; php_value/php_flag - you can set classic ini defines which can
; be overwritten from PHP call 'ini_set'.
; php_admin_value/php_admin_flag - these directives won't be overwritten by
; PHP call 'ini_set'
; For php_*flag, valid values are on, off, 1, 0, true, false, yes or no.
; Defining 'extension' will load the corresponding shared extension from
; extension_dir. Defining 'disable_functions' or 'disable_classes' will not
; overwrite previously defined php.ini values, but will append the new value
; instead.
; Note: path INI options can be relative and will be expanded with the prefix
; (pool, global or /usr/local)
; Default Value: nothing is defined by default except the values in php.ini and
; specified at startup with the -d argument
Now you can add random configuration changes such as:
php_flag[display_errors] = on
php_admin_flag[log_errors] = on
php_admin_value[memory_limit] = 128M
php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i
Of course, be certain that you restart FPM after you change the configuration so that it takes effect.