Yes I have one that you cant tell if she is in season or not, only time I knew was when I had a dog around, but I lost my last boy dog last year, so it is difficult now - men do come in useful sometimes!
Sounds to me like she has been in season, and is now just having her normal moult, plus the skin problem which is making things worse.
It may make you feel better to know that when roughs moult, they can look absolutely awful - one of mine has just started, all her undercoat is coming away from her skin and if you touch it, it comes out in your hand - and to make matters worse, she is due to be shown at Crufts in March, so I am not impressed! With regard to the discharge and the scan, it sounds to me like she may have had a rumbling pyometra, I wonder why the vet didnt mention that and spay her there and then, especially if it could have been a closed pyo, which is quite dangerous. Hope she is better soon. By the way, when you do have her speyed, she will drop her coat again!