There are a few different protections under the UCC that apply to your situation. You may be able to get out of the contract under the installment contract exception under the perfect tender rule. You may also be able to recover for the sheets that you bought in the past under the merchantability warranty or the warranty of fitness for particular purpose. You will need to find out some more information to determine whether or not you still need to pay for the damaged sheets.
The UCC allows buyers to get out of contracts when the perfect tender rule is violated. You would need to prove that CLS sent defective goods. An argument could be made that the sheets you purchased in the past were nonconforming because they often ripped when they were placed on thicker mattresses. The catalogue stated that they fit “all standard mattresses,” so they may be considered defective.
However, RRMS has an installment contract with CLS. Installment contracts are an exception to the perfect tender rule in that the buyer can only reject the installment if the nonconformity substantially impairs the value of the installment. Also, if the buyer accepts the nonconforming goods and does not notify the seller of cancellation, the contract still exists.
This is what would make getting your money back for all of the sheets that you have bought in the past difficult under this rule. Since you did not discover that the sheets were ripping until now, CLS could counter argue that you accepted the goods and did not inform them that the goods were defective. Especially since the sheets were being discarded without you knowing about it. Also, they can also argue that you accepted three shipments before notifying them that the goods were defective.
Another argument that could be made is that the implied merchantability warranty was violated. This may be a different way for you to recover for the sheets you bought in the past. You could argue that the sheets were not reasonably fit for the ordinary purposes. RRMS were using the sheets in the way that sheets are usually used and they ripped.
