Changing textures accumulate in memory. iOS.

Hello there! I am having a problem in my iOS app. Use-case scenario is:

1. user selects wc image he likes (string url is returned)

2. www is used to get image from url

3. texture2d = www.texture (something like this)

4. texture2d is applied in a gui.box in OnGUI() method.

when texture is applied, it adds 15-20mb in memory (quite a lot, is this normal?). what's worse is when user decides he doesn't like the image and chooses another (repeat steps 1-3), memory adds another 15-20 mb. so it goes to something like 40mb all in all. If user keeps on changing, the app will surely crash when going beyond 100. please tell me what's wrong, or maybe a work-around. Any guides are appreciated, thanks.