Hey, sorry it took so long for a reply, but here's what Genesis said:

Yes - you are mining BTC and getting a payout in DASH. Of course, DASH price has an impact on your payout, but much grater effect is on the mining difficulty and BTC price on the market.

Let me share some info about what events had impact on the decrease of your payouts:

• BTC price is dropping (http://www.coindesk.com/price/) - check out daily, weekly or monthly chart to get an idea
• BTC difficulty is increasing (https://bitcoinwisdom.com/bitcoin/difficulty, scroll down to difficulty history)

These events all had an impact on your maintenance fee and on your earnings. Your fee is fixed in USD, but it changes daily according to the BTC price value. The lower the Bitcoin value, the higher the impact of that fee on your mining returns.

Bitcoin price is very volatile and there can be huge differences between days. Sometimes even between hours.
Difficulty depends on the total amount of hashrate which is hashing Bitcoin. A bitcoin block is released every 10 minutes, but the more computing power there is, the more likely it is that blocks are found by those computers quicker then 10 minutes. To counter that effect, the blockchain raises difficulty to make it harder to find blocks. For Bitcoin difficulty adjusts, very roughly, two or three times a month.

We are very sorry but unfortunately, we do not control these parameters - they are variable, as so it is the sheer nature of the cryptocurrencies. As any investment, it contents inevitable risks as well as possibilities of making a profit. We hope this explains it.

Thanks for your understanding.