Kelp does not remember age value when kelp is placed and/or broken on top of it

Kelp does not remember it's set age value when another kelp block is grown/placed, and then broken on top of it, ultimately leading to a randomization of the kelp's age.

Steps to Reproduce:

1. Place kelp two blocks downward underwater
   ^{→ observe current 'age' value using F3}
2. Place another kelp on top of it
3. Break the top-most kelp
   ^{→ observe new 'age' value}

Observed & Expected Results:

- The kelps original value will be different than it's new value
- The kelp's age would remain consistent, no matter what block is placed or broken above it

Screenshots/Videos:

First age value:

Second age value:

Videos/Screenshots

KelpAgeGrowth.mp4

Notes:

This effectively allows the player to indefinitely grow kelp upwards, if they are constantly resetting the top-most kelp block's age.