areca palm & multiple problems

hello everyone,

i have an areca palm, a gift unfortunately bought from ikea. since it came to my house, it had multiple problems. it once had more than 20 stems, now only 4 left

first there was white fluffy spots on leaves. it suddenly covered all the plant in a couple of days and leaves started to die as if they were burned... i searched local markets, bought a spray and got rid of these white spots in 2 weeks. by that time the plant already lost lots of leaves.

a week later, i spotted mushrooms on it's soil! i rooted them out immediately.

then there seemed no visible problem for a while, but stems were drying and falling one by one, and i am sure the plant is not under or over watered... then i spotted brown dots coming from lower parts (photos below)

i thought maybe soil was infected, so i changed the soil 2 weeks ago. but nothing has changed. now the stems are not strong enough even to keep them straight.

i don't have much experience on gardening, but i want to save them. i tried everything i knew. any advice will be much appreciated...