I think I may have chosen the wrong LEDs - they went from bright to dark in a matter of minutes, with the cap bank stabilizing around 12.5v. I'm thinking rather than 30ma continuous forward current (100ma peak), I might want something more like 2-5ma, and/or a slightly higher voltage.
On the other hand, they'll probably very aggressively keep the caps in balance.
https://www.mouser.com/ProductDetail...rrencycode=USD
Maybe it was because it was the first time I'd charged them? I'll keep an eye on it and see.