I have been pretty lazy mining in TM and am using only one book -- mining the same spots on three different shards, so I am not that surprised that I hit a trough with an ore type and I its probably not that unlikely that we would hit the same one. The two miners I have running right now are on different sets of runes and so far they are pulling in normal amounts of shadow, if not more than usual. Small sample so far though. I will check back after eight hours or so.