You heard a bad rumor. Growers dont spray windex and other chemicals on the plant because we smoke a majority of it, and we dont want to kill of our customers. Why would we want to get sick/ get our cusotmers sick.Purposely getting our customers sick doesnt sound like a great business plan.

The reason the spliff got darker as you smoked it is because the TAR and other shit is sticking to the paper/weed. The end where the smoke comes out is becoming resinated.
(it gave you a headache because your basically smoking all of the tar and carcinogens from the tabacco and marijuana) They didnt spray anthing on there plants, that would be crazy.