Thank you Will! Now I know what's been killing my Areca.
I have covered the soil with the plastic foil to prevent the soapy water from going in there and sprayed the plant thoroughly! Do I rinse it after some time?
I also bought a special soil for palms, removed the ikea plastic pot and replanted it to the white pot you can see on the pictures. (there's LECA on the bottom) - when I was doing that I noticed that the soil was quite wet, it seems that I did not water it properly.
How do I know the right amount? Should I stick to 17 oz a week?
Once again, thanks for your reply I REALLY appreciate it