The fish move around to feed in a water column is my opinion. At a different lake yesterday it was 3' below the ice for me and in the same general area a few nights ago, it was like 4' off the bottom. The hit when it happens, is short lived, maybe 10-20 minutes. That's when I move or leave. Yesterday was the first time since late December or so that I fished during daylight. First time in since last year that I catch fish threw the ice during daylight.
I don't know where you were on Tiber but it has been slow in some places, hot in others, from hearing it locally. Seems that everyone has electronics and mark fish the whole time but don't catch. I don't have electronics other than a headlamp. I just pick a spot, drill and fish.