Those banjos with their skin heads....they just respond a little differently each time. You have to be really connected to it, or it can fail you miserably. Some days...it all just lines right up. The right amount of moisture in that head can give a tone that is unlike anything else...a beautiful resonant deep tone. It is of course, a combination of your wood and dimensions, but there are no two instruments just alike. Some days you just have to play it when it Is less than perfect. To me, this is a call to your skills to "play to it"....choose stuff that works. You can't always climb high on that thing with perfection. You just play other stuff.
We had a mean high humidty streak through most of June and into July. Even in the AC'd house my banjo didn't want to "sing" as sweat as it has. I actually sounded sad. I played it here and there, but it really did feel like I was asking it to do something it just didn't want to, so I sat it aside. Thankfully, the weather has changed and humidity finally gave up and moved on. My fair banjo came to life again or, I guess, was "happy" once more :) I think it being a tackhead had something to do with it for certain.
Waterproof them skins with an old time concoction - Aqua Net Hair Spray, or better yet, artists' spray "Workable Fixatif" or fixatif with the word 'matte, or satin, flat, etc.." It lays ON the skin, not IN it. The fixatif is a little more expensive than the hair spray but is a guaranteed flat - no sheen. If you can slip your tailpiece off then you can remove your skin, and get all the areas. You only have to do this treatment once. Both sides and all around the edge. AND, when your skin is sinking, tighten it!! The first time you tighten it is the first big stretch of the skin. On humid days after this initial tightening, loosen it a bit when putting your banjo away. But the spray really does wonders. No silicone or paste. You don't want to condition the skin, you want to seal the surface.