iOS memory inconsistent between builds

I'm sure this has come up before, but I am having difficulty searching the net for this issue. I have a game on iOS and Android which uses a lot of memory. I have done some optimizations like reducing texture sizes and disabling objects which has helped a lot.

The thing that is confusing me right now is that if I build and run my game one time, it will use as low as 210MB of RAM, then without making any changes, I build and run again with up to 340MB. I know that 210MB is still a lot for a mobile game, but why is there such a fluctuation in memory usage? It makes it very difficult to measure the effectiveness of further optimizations. Any input would be greatly appreciated. Thanks!

PS. I am running Unity 5.1.2p3 using the old networking system. This is an MMORPG with hundreds of enemies (hence the massive memory usage). If it help to see the game to pinpoint the problem, it is available on Google Play and the App store under the name "Lunatic Fatali".