I can confirm this. My kelp farm no longer produces anything.
I ran a test by planting some kelp in water and watching and after half hour, none have grown.
Basically destroys kelp as a useful item in this game now.
Had this just happen to me on my Xbox X. I'd destroy chests and the items in them wouldn't appear. Had to do a hard reset and reload the game in order to get the items to appear properly.
I can confirm I have this issue with the latest beta version on my Xbox One X
I have the same problem - there should be an option to control the spawn rate (low, medium, high).
I can confirm this. I thought it was the way MCPE worked though?
Noticed same issue. Kelp is now no longer a useful product in MC