i dont recommend feeding dead feeder just cuz they get pretty icky. but invest in a little 5 gallon tank and house a few dozen crickets at a time with egg crates and fresh fruits and veggies for them to eat and they should last weeks until you can feed them off to your cham.
I would also be cautious as you don't know what they died from. I just toss them and go buy new ones. No problem in making him wait a day so you get new food instead of giving him dead food that may have had issues....