Lurcher eating mud!

[poochuspoochus]

My twelve year old lurcher has started determinedly eating what appears to be mud when out on walks. It may be roots or dried leaves that are in the mud that's she's actually eating. It's making me worry that she's missing some mineral or something since it's a relatively new habit. Other maybe relevant things. She's always been obesssed with food the whole nine years I've had her. She had got a wee bit chunky but has slimmed down slowly since the summer to a good weight by just cutting out all extra extra treats and splashes of milk she was managing to cadge off people. She has been taking vetmedin for a heart condition for the last 3 months. I also thought maybe she was seeking out vegetable matter because she was missing her daily carrot she used to get, the vetmedin has to be taken on an empty stomach so sometimes timings don't work out and she can't have a carrot but there is veg in her dinners. She eats well and has a decent diet I think. She's seems well and her coat is glossy. If it's just her her new hobby I will just continue to try and deter her and not worry about it but does anyone think it might be a sign of her needing something she's not getting?
Thanks for reading all that!