The earth tower on aprentice (4th tower) deals no damage to enemies, played it in a few maps and, the animation plays, it LOOKS like it deals dmg to them, but no, i decided to playtest it by losing the round on purpose but only after i placed a good 7 of them in one lane and tested them against a unit.
When inspected they dealt 0 dmg. upgraded to last tier and same thing. enemies just as healthy as when they spawned, and no its not lack of damage
I was able to reproduce this. Thanks for the report!