If the kits are new, ie: you just bought them, take them back and get them replaced with kits that are still suitable and haven't expired. If the shop won't replace them, send a copy of the receipt to the manufacturer (API) and ask them to replace them.
Test kits last best when kept in cool dark conditions. I keep mine in a bucket in the fridge, or the door of the fridge. Make sure children can't get to them because most contain toxic chemicals. Wash your hands well with soapy water after handling/ doing water tests.