Important: The rewards are calculated in blocks, not actual time.
Every 432 blocks, you can claim 0.1 $POTATO for every Farmer.
Every 432 blocks, you can claim 0.05 $POTATO for every Farm Girl.
1 block is about 2 seconds. Since blocktimes are slightly higher recently, this results in slightly less $POTATO that you gather daily. This is the same for everyone, you are not the only one getting less rewards sometimes.
As more characters are introduced, this section will be updated. The exact rewards for pigs, cows and other characters will be disclosed at a later point.