Android app crashing on mobiles with 1gb Ram

Hi - I have built an AR game (using vuforia plugin), where in my second scene, I am setting up 15 targets and 15 3D models (one for each image target). Overall 3D models size is 40mb, and my apk size is close to 70mb. App runs perfectly fine on Mobiles/tablets with > 1GB ram, but it is crashing as soon as I load my second scene on Moto G and other 1GB ram mobiles. Initial loading time of scene-2 is around 40-45 secs on most mobiles. When I reduce the models to 7 (from 15), app starts running on Moto. Also, initial loading time comes down to 15-20 secs.

My Setup: - Unity 5.2.1 - Vuforia Unity SDK: 5-0-10 - Moto running Android Lollipop 5.0

My question: While preparing to load a scene, is Unity using cache or RAM to load up all models in the scene? And is there any way to reduce early load on memory and make my set-up work on 1GB Ram mobiles?

Note: - I have already gone through troubleshooting Android builds and there is no native incompatibility. It appears to be a RAM usage issue - I have a work around in which I can build scene-3 and take half the models to scene-3. But that would add another switch of scene button on UI and would not be an ideal user experience.

Would highly appreciate any feedback from this amazing Unity community. Thanks a lot in advance!