how long have yo had the plant for ?

most likely your letting it dry out for too long between waterings how often do you water?

looks like your watering it in the sink thats the way i water my ficus too i let the water sit in room temperature for at least 12 hrs and i water so that plenty of water drains from the bottom

This post was edited by Hrose on Mon, Jan 13, 14 at 14:12

Have you ever thought of watering with distilled or rain water?
Did you say the 'dirt' was heavy?

Mine is very sensative to dissolved salts whether by fertilizers or tap water...Mine use to scar like this until I resolved it.
Also too, they are easily prone to root rot if the mix is too wet for too long or dried out to long before waterings..
This too can mar the leaves like that.