... If you send the other 2 units back to us we have no problem replacing all 3 of them. Normally returns would be handles by the retailer ...
Sounds very fair to me - you have had only 1 failure, but they are willing to replace all 3. All that you have to do is send them your address and your new elements will turn up.
Good way to allow the wholesaler to prove to you that their new design has resolved the problem.