This is how the leafs look like. I already cut 2 because they died :(

Looks like the air is too dry, especially if that heater it's beside is turned on. The little 'bubbles' is slow release fertilizer usually put in the pot before the plants are shipped out of the nursery. I would repot the plant to a slightly bigger pot with a good potting mix and try and increase the humidity. Maybe you can spray the fronds with a mister a few times a week. Also are you sure this is a Kentia palm? It looks like a majesty from the pic.

I think you're right, the air is dry. Maybe the spray will help, I'll give it a try. I also noticed that the roots are still not strong, and the plant is flimsy, as if it didn't suck any water at all since I bought it. I didn't know exactly what type of palm it is, but I searched now and you're right, it's a majesty. Thanks for the tips!

That is not a Kentia palm. That's a majesty palm that is sold at home depot and lowe's. The gray granules are slow release fertilizer. This is not an indoor palm.