Question: I have been mining for a short while and my payouts have been XX every 24 hours. The last day or so my payouts have decreased to XX every 24 hours. Why?
Your payout relies on a few different things. Most importantly, the number of shares accepted by the pool. If the number of shares being accepted hasn’t changed, take a look at how many blocks the pool has found over the time period where your payout has decreased. If the pool has found less blocks, you’re going to see less of a payout. This is based on luck. If the pool you’re using has found more blocks than usual, you should be seeing an increase in payout. If nothing has changed and the pool has found the same amount of blocks over that period of time, you may want to contact the support team of said pool as there may be an issue.
from here