Totally agree on composites holding up better. When we redid ours, we went with composite shims after my brother warned me about plastics cracking in ...

True, snakes def do the job, but honestly I've had pretty awesome luck with baking soda and vinegar. Let it fizz for a bit, chase it down with hot wat...

Haha, I feel your pain! Had a similar issue a while back, drove me crazy for months. Turned out the culprit was actually mineral buildup in the pipes ...