Balance comment. Not sure if this is a mistake or a deliberate choice, but a few items feel like their upgrades are obviously stronger than others.
All the "+2" bonus items give an additional +1 per level, functionally halving the value of their upgrades over grabbing a different base level upgrade.
Staff of forethought has 25% chance of activation at first, then goes up to 50% on the second upgrade, which is the full value added again. Its final tier jumps it to 100% activation, which is a double-strength upgrade.
Similarly, the Bloodthirsty Dagger has a 33%/66%/100% scaling of its effect as you level it up, progressing linearly at the same rate as its initial effect. That said, this one feels quite weak when you first grab it, but becomes notably more valuable with its upgrade steps.
The Grass Crown is a 75% bonus effect, which then jumps to 150% then 225%, again, progressing by doubling then tripling the level 1 effect with additional levels. This makes those flat +2/+1 modifiers feel like they fall behind when you're upgrading them.