Ok long story short, I have a guy that just got his license to do turf apps. He has helped me before and I hope to have him doing apps full time next season but until then we are both going to spray when we have free time from mowing. I have a 200 gallon Lesco skid sprayer and decided to buy the same setup for him to use. I helped him get it all wired up and loaded it onto the mowing truck and filled it with water. I helped him get it calibrated and showed him a few pointers then I told him to practice around the parking lot at the shop with it to get used to everything. Once he ran out all 100 gallons I told him to put the products I had set aside in the shop in the tank and fill it back up. Well he thought he had it down so he went ahead and put the chemicals in and started spraying. My question is the propylene glycol that they put in the tanks to protect them what is affecting the lawns? He says he had maybe 60 gallons of water left in it when he mixed it. The next 3 tanks of chemical look good, it is just the first apps that he did. Is the glycol acting like a roundup? What can I do please let me know what you think.