The symptoms on your fig may be cultural. The brown edges could be the result of chlorine and/or fluoride in the water. Many houseplants are endemic to the tropics and are sensitive to salts and other chemicals used to treat our water. Try using distilled steam iron water or let tap water sit in an open container overnight so that the chlorine will dissipate. Also the fiddle leaf fig should not be overwatered – water only when the top inch or so of soil is dry. Raising the humidity may help – set the pot on a tray of gravel and fill the tray with water (but do not let the pot sit in the water as this may lead to root rot). Feed with a slow release or organic fertilizer formulated for container houseplants and try to stay away from chemical fertilizers that are high in nitrogen and salts.