Ah sadly you are seeing the same thing I use to deal with but not as bad. I use to recall waking up and finding almost half my mining returns where now gone in less than a weeks’ time. It’s like an arms race and people keep adding more and more mining. When new things come out and the first ones start to get mailed out you can see in less than a week a massive decrease unless you as well spent the same amount just to keep up.
Some people take on far more risk than just trying keep up in the race. They will mine x amount of low priced coins then sit on them. If that coins price ever skyrockets they just hit the jackpot as they will have massive amounts of those coins. If not they had a very bad week/month/year.
Someone out there is making a massive killing on mining. It’s just not me. I’ve tried it in the past. Friend of mine even wanted me to help him get into the game of mining. He was a bit shocked at barrier to entry and the fact the he would not really be mining bitcoin since that’s not the way to go for someone just trying to enter in.