Strange low volume issue.

Hey all. I haven't seen any post from any other users about an issue I'm having lately... Beatmakers overall volume appears quiet recently for no apparent reason. Used to have my headphones volume about 75% for fairly loud audio whilest making my drum and bass but very recently I have to have my volume on 100% and it still isn't loud enough. I use beatmaker to control sunrizer and animoog in real time using virtual midi and their volumes are still very loud in comparison. I've tried everything I can think of to sort the problem. I even updated to 2.4.2 as I had 2.4 but alas I have the same problem. There's no compressors running on master buss. Phone volume on max, volume inappnis on max, audio setting is also on max. I'm all out of ideas and need some help please. Thanks

Edit to add: sorry forgot to say I'm on iPhone 4s 5.1.1