Is there any way to report a problem on an app that appears to be no longer supported

I'm not even sure this is the right forum to post in but how do you alert Apple to apps that no longer seem to work to their full extent?

I've got an app where the in app purchases can no longer be bought, the support page takes you to dead page, and the email address no longer works. The reviews from the last few months are from others all experiencing the same problem and there is no option on the iPhone or in iTunes to 'report a problem'. I have tried the Apple pages and it keeps taking me in circles. I've tried the 'support' page, gone via the purchases pages etc, but can't find a way to actually notify anyone that this app should really be removed from the store if most of the features can not be bought and it has no support.

The app is the RHS gardening app and is a free download, but without the in app purchases, there really is little use for the app.