You said the humidity was good per the meter? I'm not sure how they could dry out if so... The packets are completly safe. Sometimes it takes a few per jar, or they don't keep up. Now, I put at least 2 if not 3 in each jar (of the 2" packets). I've not had this issue before. The packets will stiffen up when they are "done". Are they stiff at all? They shold still feel like they have "water" in them almost, not thick pudding. If that makes sense. I've got some that are just now starting to get firm, but most have lasted 6 months no prob. They definitely don't last forever, though.
For longer term, I've started vacuum packing my jars with a Food Saver vacuum machine and a mason jar attachment that you can get - allows you to do a good vacuum pack with any wide-mouthed mason jar. It's freaking awesome - I LOVE that thing - I vacuum pack everything now. You can even take a partially opened bag of chips, stick the open end in the machine and reseal it (with or without vacuum). No more chip clips!