I've fallen into this trap a few times now, especially when away from pc and only checking blockfolio. What happens is I'll buy an altcoin (let's say KNC) with bitcoin and then load that altcoin into blockfolio and update my holdings.
A few weeks / months later I'll check my KNC holdings and see that it's up 22% - nice.

However, if I switch to BTC value I can see that I'm actually at a loss on the trade...

I bought KNC at .000158 BTC and it's current value is .000136 BTC, so my KNC trade is clearly not doing well.

The only reason it's up 22% in the first picture is because bitcoin is up. What I'm seeing is the difference between the higher bitcoin price and the lower KNC price, which in USD still results in a net positive. This is a bad trade indeed, as my money would've done better just staying in bitcoin.
Make sure you're tracking your altcoin trades in the currency pair you bought them in
.
A few weeks / months later I'll check my KNC holdings and see that it's up 22% - nice.

However, if I switch to BTC value I can see that I'm actually at a loss on the trade...

I bought KNC at .000158 BTC and it's current value is .000136 BTC, so my KNC trade is clearly not doing well.

The only reason it's up 22% in the first picture is because bitcoin is up. What I'm seeing is the difference between the higher bitcoin price and the lower KNC price, which in USD still results in a net positive. This is a bad trade indeed, as my money would've done better just staying in bitcoin.
Make sure you're tracking your altcoin trades in the currency pair you bought them in