MU .htaccess

I have a multisite WP install that is working fine, but I’ve recently discovered that not all of my .htaccess settings are applying across the sub-domains. Some seem to be, like those dealing with the rewrites for the post and page links to look pretty, but this one for gzip compression

<IfModule mod_gzip.c>
mod_gzip_on Yes
mod_gzip_dechunk Yes
mod_gzip_keep_workfiles No
mod_gzip_can_negotiate Yes
mod_gzip_add_header_count Yes
mod_gzip_send_vary Yes
mod_gzip_command_version '/mod_gzip_status'
mod_gzip_min_http 1000
mod_gzip_minimum_file_size 300
mod_gzip_maximum_file_size 512000
mod_gzip_maximum_inmem_size 60000
mod_gzip_handle_methods GET POST
mod_gzip_temp_dir /tmp
mod_gzip_item_include file \.html$
mod_gzip_item_include file \.php$
mod_gzip_item_include file \.pl$
mod_gzip_item_include file \.rb$
mod_gzip_item_include file \.py$
mod_gzip_item_include file \.cgi$
mod_gzip_item_include file \.css$
mod_gzip_item_include file \.js$
mod_gzip_item_include mime ^application/javascript$
mod_gzip_item_include mime ^application/x-javascript$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include mime ^httpd/unix-directory$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include handler ^server-status$
mod_gzip_item_include handler ^server-info$
mod_gzip_item_include handler ^application/x-httpd-php
mod_gzip_item_exclude mime ^image/.*
</IfModule>

It works perfectly … except it only works for the main domain.

if you check services like YSlow https://universal-nexus.com is using compression, but none of the sub-domains are https://jblog.universal-nexus.com https://h2g2.universal-nexus.com

I can’t find any other .htaccess files that would correspond to the sub-domains (and didn’t really expect to, but I wanted to rule out everything), and Google is proving to be no help since most questions about .htaccess and MU configs relate to the mod_rewrite bits.