dropped mining reward 15% is not much ser, if you mining quite long enough this is normally happen, even single week can drop 70% on some coin because the project get awarness
in big miner, or some influencer start talking and difficulty jump to much cause crowded miner began hitting the network blindly
a 15% reduction in the mining reward is still tolerable, but when the profit drops by 70% due to new miners, then it’s time to look for a new coin. But Nice Hash will not allow your profit to drop much and will switch your equipment to more profitable coins.