Caution about water tanks

I've had 2 units for about 2 years now and I've been happy with the product. However, recently within two weeks of each other, both water tanks need to be replaced. The first one has a lined crack along the unit and the second one shattered into several pieces. Notified Kaz and ordered replacement tanks (w/o caps) $12 each + $6.95 (shipping). They said that there were no other similar occurrences. Perhaps it was the unnecessary Protec cleaning cartridges placed into the tanks. I just wanted to put it out there that the tanks might be harmful. I'm still ordering the tanks because I like how the product works and since this seems to be the most cost effective method unfortunately, and cross my fingers that these new tanks won't break!