Yikes. Open your closet door like, now, and get fans going. That plant is suffocated and may not recover. I would tell you to flush it right away to get all that nitrogen out of the soil that is contributing to the dark, dull leaf appearance, but unless your soil is quite dry at teh moment, don't. If it IS nice and dry, pour about a gallon of plain tap water through the pot.
That sudden turn for the worse makes me think that when your friend told you to add more water, it was too much, and you have now added root rot to the list of problems.

What size pot is it in? If you HAVE to do anything to save that plant, get the next size bigger pot and one bag each of unfertilized 'seedling starting mix' (there is a reason for this I will tell you in a minute) and perlite. Mix to 1/3 perlite and 2/3 seedling mix. Re-pot into this VERY LIGHT medium to let the root ball dry out if you have rot conditions, and keep that closet door open!!!!

Okay... why seedling mix. This is because at box stores, most of the potting soils are prefertilized and harsh and seedling mix is either completely unfertilized, or it just has a little bit of phosphorous in it for root growth, which is fine for a flowering plant. Why perlite? Because you are trying to increase air flow to ALL PARTS of your sick plant to save it, not just the leaves. Perlite adds some serious fluff factor to the dirt and can be a lifesaver for a sick plant.

You got your projects... now GO GO GO because that plant doesn't look like it's long for this world!