Tracee, what kind of smell is it when they are "off" ? And is it O.K. if they are a little dark?
I know I'm not Tracee but............
If they are "off" they stink like rotten meat, you will know it if you smell it
When pinkies are thawed it's quite ok for them to go dark, this is because their skin is still quite transluscent when the mice are this young and you can see the blood through the skin easier.
I thaw all my mice the same, put them in a plastic container, run hot tap water over them and fill the container, pop a lid over the top and leave to sit. Pinkies take just a couple of minutes, large adult mice can take 15 - 20 minutes or so. I check they are defrosted properly by giving them a gentle squeeze all over, making sure you can't feel any ice crystals or cool spots, especially in the stomach, chest and head area, if there are cool areas or you can still feel ice crystals, repeat the process, when they are warm throughout, they are ready to feed.
Sometimes, young corns prefer their pinks to be heated a little more, so if I have one like that, I just run the water hot again and let it sit for another 30 seconds to a minute before offering straight away
Hope that's helpful,