This is the thing the pulley's engage the belt perfect and it was never over tight - even on my last engine i had a cam cover leak but i have a cover over the pulley's so couldn't see and that belt was fine but so they say the issues i have suffered with a complete delamination on virtually every tooth points towards contamination.

Although i have learnt a few things from this and thats to make sure the engine is keeping it's fluids oil and water and to regularly check the belt - i'm even thinking about fitting the cover back on as their's a possibility something may have found it's way in causing this i'll never know.