2 sisters in a pot

So I've added some soil on top while it was growing in week 2, I always do that to make sure the stem is stable and supported by the soil. But I took soil from the pot where previously I've added ground coffee. And that coffee powder messed up 2 of my other plants in the past. I was adding it because everywhere internet says that adding this improves the growth and contains lots of nutrients. I've seen many youtube growers using it. For me it didn't work at all and I very much regret using it, messed up so many of my plants and wasted so much time. So because I've added the soil from the pot that still contained traces of it, even though I removed the most part and thought it wouldn't affect what I get is completely stunted and dying plants on week 5.