A couple of updates on Frank.
First, he ultimately was not a big fan of the freeze dried ferret food. Even when I broke it up more, I don't think he liked the consistency. So, I went back to the normal ferret pellets (dry then soaked in water) with his veggies and fruit and an occasional canned or live insect.
Secondly, he started brumating a few weeks ago. He hasn't eaten much at all, but I still offer weekly now, not more. He's also hiding most of the time and occasionally will come out to drink and he's had a few urines in the past few weeks and only one poop.
He did this last year as well and it's normal as they mature for this to happen. I let him do it and do not force the issue either by bothering him too much or adjusting temps to encourage it.