Mate, if it was me and the same two players were wiping me out every month, then I’d yank them. Albeit only two (2) players it’s hard to gauge. But, my line of thought is, if I send more players and the same is happening in 6 months time, then what do I do. Sometimes it’s better to cut your loses early and promote someone else, especially if you hold doubt toward their honesty.
Stuff like this can be really stressful, especially when you hold doubts to the programs cred. It turns into you checking stats 3 or 4 times a day and being super paranoid. Honestly it’s not worth the stress. Far better to cut the loses and promote someone else 
If you never make jack and these players keep winning then you’ll know you did the right thing. If hoqwever they start losing and you make money, then you could probably risk giving them a little space but don’t got crazy with promoting them. Just see how it pans out.
Cheers
Dave