Tracking 25 VuMarks

I have been working with Vuforia for a little while now. I am trying to make a grid of VuMarks. I can get all of them to track and I can get the string I want out of them but once the objects are lost and found a couple time the whole app crashes. It seems to become a problem sound 15 targets. I am going to try a more powerful machine and see if there is a difference. I do not think anything will change though because it seems to behave the same way on my test phone . If anyone has tip on tacking more than 10 targets that would be awesome. I saw somewhere that I should be able to track around 50 at once per database.