Nothing is wrong.. Nicehash is the marketplace.. get that! They need a person who will BUY your hashing power.. and if his/her highest bid is everyday lower.. you will get lower reward... easy as that...
You are not mining BTC or anyother coin on nicehash.. you are selling your hashing power to the highest bidder..
Is this why NiceHash sometimes switches to algos that are clearly not the most profitable at the moment? For example, I am doing a comparison between it and Nemosminer on MiningPoolHub with both getting a single GTX 1080 and I just caught NH switching from Equihash - which was projected to earn $4.31 per day - to Nist5 - which caused projected daily earnings to plummet to $2.10. Based on what you wrote my theory is that there wasn't enough Nist5 hashpower available to fill outstanding contracts so miners got switched to the algo even though it wasn't even close to being the most profitable.
No, Nicehash switch algorithms TO the most profitable at the moment.. If you "benchmark" all algorithms in their program, it will be switching between all.. If you know which is the best or the most profitable algorithm for your GPU, go and uncheck the benchmarked algorithm there and the program won't be able to switch.
NH swithes if there is the better offer on Nist5 even if it last only for a 10 mins... It was the most profitable for 10 mins.. and thats why it changed..
Thats the stupides thing I have ever seen, because you are basicly losing time with switching every 10,20,30 mins...
Solution: Uncheck the all algorithms except the most profitable.