The law provides that anyone who furnishes labor or materials to your home can record a "Claim of Lien" or "Mechanics' Lien" against your home if they are not paid. Even if you have paid your general contractor in accordance with the contract, if the contractor failes to pay any subcontractor or materials supplier who performed work or supplied materials in connection with your project, you still run the risk of having a lien filed against your property. You could be required to pay a bill twice to keep from losing your home in a foreclosure proceeding.
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Looks like they are a subcontractor that didn't get paid by the contractor, and judging from the numbers, they are putting liens on EVERYONE.