Replace "small life" with "some pests" in the description of the pestilence activation.
Use "becomes pale" rather than "glows pale" in the mana ball activation. For something that's closer to the original translation but less awkward, "glows faintly" or "glows palely" would be alternatives.
The english-object-activation-edits branch, https://osdn.net/projects/hengbandforosx/scm/git/hengbandosx/commits?branch=english-object-activation-edits , on the hengbandforosx project (branch is based off Hengband's develop branch) has some commits for minor changes to the English messages from src/object-activation: