First off, it doesn’t matter, plastic takes decades to break down. Secondly, plastic is not replacing silicon because plastic is not a conductive material like silicon is. There is some research into other materials than silicon being used, but so far are not commercially produced. Those could have some organic materials in them that can contaminate soil. Sorry, no matter how much you want solar panels to break open and contaminate the ground underneath it’s just not happening.
I understand some of the large farms have series of pipes circulating different chemicals, including water in some cases, for cooling effects. But this is different than what you are describing. Perhaps you misunderstood. Or maybe whoever you got the info from was wrong or just flat out lying.
Plastic is a cover/a shell/a panel of sorts like TV panels and the stuff inside can get exposed a storm, if something like say a tornado hurls debris which penetrates the shell, exposing the innards which rain carries to the ground.
Well it does happen frequently - no matter what you care to imagine. Just the cost of doing business on big solar power farms.
Blaming the messengers is always an excellent way to deflect and discredit.