I started mining two months ago and within about two weeks of starting I ramped up to 5 GPUs. My first 3 payouts occurred about every 10 days, but the last two have taken 12 days and now the portal shows 14 days until the next payout. My reported hashrate has not changed. I assumed that as difficulty increased hashrate would decrease and it would take longer to payout. But since my hashrate is the same I'm not sure why my payout is different. Is the cause the increase in difficulty? Thanks.