What specifically do you mean by having a hard time reading the cards? These things rarely wear out, although they can fail. If they do fail, they would likely not work at all. If this is happening with more than one card at
the same time, it's probably something other than the card.
Make sure it is not the computer. Reboot and see if things work better. Try another computer. If the problem does seem to stem from the computer, are you running some form of antivirus (with current definitions)? Rule out the reader if you can, by borrowing someone elses. I have seen issues where cheap readers will work sporadically.
Counterfeit cards show up on reputable sites like
Amazon from time to time. It's not the fault of Amazon or E-bay, it's the disreputable vendor. Most of their cards will work, some will work inconsistently.
Where did you get the cards you have? If they came with the camera, or from a nationwide department store, or online and you paid fair market value, they are probably genuine cards.
Having spare cards/readers is never a bad thing, but if it doesn't solve your problem, it's not a good thing either.