Random objects appearing on top of each other!

Hi, if someone can look into this file, the issue I have is random appearance of objects like �Planks�, �bombs� and �bottles� sometimes they appear too close to each other or ontop of each other..how can I stop this creation of random elements not to collide with each other..i have used a couple of techniques but not very effective.

Here is the link to the capx file.

dropbox.com/s/cgnlat9j1ja24nv/hydraman.capx

Thanks in advance for your support in this.

Ameer.