Ficus lyratas are not particularly fussy about their potting mix as long as it has the standard amount of porosity. However, I am not convinced that repotting it is necessary. If you water thoroughly (until some water trickles through the drain holes) and that keeps the soil moist for at least 3 or 4 days, then you don't have to worry about repotting.
Some of the information you provided suggests that you may not be providing an ideal amount of light. Lyratas do just fine in direct sunlight in most home environments. Corner locations in well-lit rooms usually do not permit enough light. Likewise, Lyratas that are located off to the side of a sunny window usually do not get enough light.
