Not Cathe here.
If you are losing defintion, perhaps either (1) you are gaining weight so the muscle is being obscured or (2) the muscle mass is decreasing.
Suggest you review your diet. Re. (1), Perhaps the increased exercise load is causing you to eat too much of the wrong thing. Re. (2) perhaps you are not ingesting sufficient protein to rebuild muscle mass after the increased level of strength training. If so, then the body, needing protein, finds it by taking it from other muscles (reducing them) or just doesn't rebuild at all.
Another thought just occurred to me. Perhaps the change in routine is leading to long lean muscle mass rather than the larger type of muscle that occurs after heavy resistance strength training. You would need to analyze the strength training you are doing to determine which type it is.
Good luck.