Cache-control headers

I’m trying to set the cache control headers, i tried the slim/http-cache and a few other options, but i cannot get a cache-control enabled. the browser keeps adding a line:

Cache-Control:no-store, no-cache, must-revalidate, post-check=0, pre-check=0

so the cache does not work, this used to work fine in slim 2 its basically the same application.
to make things more clear i setup a middleware route:
public function __invoke($request, $response, $next)
$response = $next($request, $response);//execute the transaction
$response = $response->withoutHeader(‘Cache-Control’);
$response=$response->withHeader(‘Cache-Control’, “max-age=2400”);

    return $response;

but this does not remove the cache-control line.

my htaccess looks like this:
Header always set Access-Control-Allow-Headers "Origin, X-Requested-With, Content-Type, Access-Control-Allow-Origin, Accept"
Header always set Access-Control-Max-Age "1000"
Header always set Access-Control-Allow-Methods "HEAD, PUT, GET, POST, DELETE, OPTIONS"
Header always set Access-Control-Allow-Credentials "true"
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.)$ %{ENV:BASE}index.php [QSA,L]
RewriteRule ^(.
)$ $1 [R=200,L]

what part am i missing?

thanks for your feedback,

kind regards,