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Call the waste water treatment plant.

From my experience, removal of old landscape cloth is not easy, and can be very frustrating!

I would gather shovels and garden forks and it is a matter of learning the best technique.

The landscape cloth can be hand pulled but generally tears off in pieces.

There are a number of diseases, pests, and environmental/care conditions that can cause this. The following article explains some of the possible causes:
https://www.rhs.org.uk/Advice/profile?PID=132

Check your hedge for any visible pests, such as aphids or scale insects. Also, make sure you are not pruning the hedge too hard, since this can cause dieback.
https://www.rhs.org.uk/advice/profile?PID=352
https://www.bartlett.com/resources/Browning-of-Leylandii-Hedges.cfm

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This would depend on the chemicals used. Soil tests would be able to determine the soil contents.
Talk to your County Extension Office to set up soil testing.
Here is a link to help you locate your nearest office.

https://www.gardeningknowhow.com/extension-search/

It depends what type of plants they are. Some flowering plants naturally have thick stems and need them to support themselves. You might be able to prune the plants back and get thinner stems to re-grow (at least at first), but check the pruning instructions for the varieties you have.