My game crashes on iPad2, please help

iPad2 is the oldest platform where our game should work.

The game is an interactive book, with some textures and planes and some minigames.

It crashes at random points after some minutes running.

This is the last output Xcode gave me after a crash:

Unloading 0 unused Assets to reduce memory usage. Loaded Objects now: 6002.
Total: 94.270958 ms (FindLiveObjects: 2.170041 ms
CreateObjectMapping 1.810750 ms MarkObjects: 90.010582 ms
DeleteObjects: 0.271541 ms)

2017-02-08 11:37:04.042 mydestiny[489:18791] Received memory warning.
WARNING -> applicationDidReceiveMemoryWarning()
...
UnityEngine.SetupCoroutine: InvokeMoveNext(IEnumerator, IntPtr)

(Filename: /Users/builduser/buildslave/unity/build/artifacts/generated/common/runtime/DebugBindings.gen.cpp Line:51)

The important line is:

WARNING → applicationDidReceiveMemoryWarning()

You are out of memory. The iPad 2 has 512MB of RAM, but you can probably only use about 256MB. If you profile your game in Unity you can look at the memory stats to get an idea of what is taking up the space.

A good thing to check first is the size of your textures.