Think you're correct in assuming the higher RH of your stash is the issue. Couple reasons why, but don't think any need for that discussion here.
I also use the 62% Boveda packs and have run into the same issues - sometimes at least. I've had trouble finding the 58% Bovedas (think there are some lower ones, too), so just use the 62%. But, haven't looked for lower percentage ones for quite some time.
Sometimes, like in winter for me when it is much drier in the house, I can leave a nug or two out on a tray with a piece of paper or something over it for a few hours or even overnight. This will dry it out a little (55%? probably there or somewhere close). Makes for better/easier grinding & vaping.
But this time of year, RH in my house usually floats between 55% - 75% depending on weather outside and how often I feel like I can afford air conditioning.
This trick usually works well for me. Take a nug or two (whatever you plan to use in next few days) and loosely wrap it up in a plain piece of paper, or a piece of a brown paper bag. I just make a little envelope with folds that would hold about twice as much as I'm trying to dry. Put this on top of your cable converter box (or stereo that's on, or other electronics that get warm), on top of fridge near the back, in front of a sunny window, or wherever it will get just a bit of dry heat, for an hour or two. This should dry it out pretty well, even when humidity is higher. IME this will do well If humidity is up to about 80% (as much as I can stand before A/C goes on!).
Or, do the same with the envelope and put it on the dash of a closed up car in sun. I'll usually only leave this for 1/2 hour - 45 minutes. Never more than an hour depending on your particular situation because it will start roasting slowly. Be forewarned.... if you do this, the car is going to be smelling a little too sweet until you can air it out. Just open the windows for a minute or two while moving, or 1/2 hour or so if sitting.
I then grind this little bit up and put it in an airtight jar. Keep that in the dark, and away from high heat. When you pull some out, get the jar opened and sealed back up as fast as you can. If it gets humid in there and you start to have same problems, put material back in paper and re-dry. Find this works pretty well if needed, especially if you give it another quick grind before use.
A little heat goes a long way here! Don't be tempted to take it too far and pop it in the oven, or to use aluminum foil instead of paper. It can be done, but is much trickier and requires a close eye on things. Stick with the paper and longer times if you can.
EDIT: Looks like 58% Boveda packs are now
available on Amazon for same price as 62%. Seems most agree best RH level for long term storage is 59% - 63% (all over internet), so I'm sticking with current method and drying above. Don't see the need to get 58%, even for material that is in short term storage. That seems like it still will be a little too moist for my liking to vape, so still have the issue of having to dry a little before grinding.
