First don't panic. Even if your mulch was made from recycled wood products with "chemicals" they would not be causing the quick death of your plants. It is more likely that your plants are dying from thirst as you may not be able to see how dry the soil is below the mulch and the wood chips are keeping the water from getting to the roots. I would allow a slow running the hose to soak the soil under the mulch around each plant. See if water perks things up. Do not remove the mulch as it does help shade the soil and hold moisture. I would keep the mulch and allow it to break down over time. I assume you are not using it around edible plants but rather trees and shrubs in the landscape. Keep growing, Marianne Binetti