From my game play observations:
While each bloomerang can hit a target twice (when going forward and then backward), those two hits combined, deal about the same amount of damage as a single pea from Peashooters. Thus, each boomerang can be considered equivalent to one pea, but can hit up to 3 targets - so equivalent to 3 peas if you have 3 or more zombies in one lane.
Plant Food:
When overcharged with Plant Food, Peashooters shoot approximately 20 peas a second for 3 seconds, that is 60 peas in one direction.
Bloomerang shoots approximately 10 boomerangs in all 4 directions when overcharged. That is equivalent to 10 to 30 peas shot to EACH direction when you have 1 to 3 targets.
In conclusion:
Peashooter: 60 peas in one direction.
Bloomerang: up to 30 peas-equivalent in one direction (if you have 3 or more zombies), theoretical max is 120 peas-equivalent in all four directions.
So without considering other situations such as grave stones in the way, or a really tough zombie in front protecting annoying zombies, it seems like you should feed a Peashooter for its maximum fire power.
Best Answer
Try "restore purchases" from the main menu -- it's a longshot, but possibly that could shake it loose.
If not, sadly you may have to start over as a new user. I couldn't imagine playing without the kernelpults.