The income is related to your own computing power and the difficulty of mining on the entire network, both of which will affect the mining income.
First, check whether there is an abnormality in your hashrate;
Second, it depends on whether the difficulty of mining across the network is rising. When the market is good, the number of mining machines increases, the computing power of the entire network continues to increase, and the corresponding mining difficulty is also increasing, so the mining revenue will decrease day by day, and the duration will be related to the market, which can be as long as several months. And vice versa when the market is not good, more coins will be mined every day.