Unexplained Skin Nodules

My active 15 year old Dapple Gray TB mare has rainscald across her back and shoulders. Recently she has developed 2 small, solid, red nodules/lumps in close proximity to one another on the skin surface above her hip . They do not appear to be causing pain, discomfort or itchiness to her, however i am still concerned.
I have tried betadine wash and quit-itch shampoo in hope that it would cure/minimise both conditions with no avail. Does anyone have any ideas about what it might be?

[lindasp62]

Rain Rot or Rain Scald is a relatively easy sking condition to prevent.  It is a condition that appears in a horse that is outside a lot and that does not get regular grooming or bathing. Rain, high humidity and moist conditions facitlitate growth of he organism dermatophilus congolensis. It is caracterized by scaly patches and hair loss.
Fortunatly, it is easy to treat.  A gentle bath with a shampoo such as Malaseb will get the organism under control and loosen the scabs.  the scabs can be painful, and a a twice or thrice weekly shampoo may be needed to get the condition under control.
After that, regular grooming and weekly bathing will prevent further episodes.
Does your horse have shelter?  Something other than a tree?  This is necessary not only for the elements such as rain that can lead to Rain Rot, but to get the horse out of the elements in general (shade, thunderstorms, etc).
As for the nodules...hard to say.  Grey horses are more sensitive to the sun's rays than other colored horses, so it would be best to consult the veterinarian on this to see if it is something caused by the sun or what it may be.
Grey horses can be pre-disposed to Melanomas.  Many are benign and can occur under the jown line, at the anus, or other places. A veterinarian will be able to advise you on this as well.
I hope that this has been of some help. Let us know how your mare progresses.
p.s. I would advise washing all your brushes and curry combs  with the Malaseb when you shampoo your mare, otherwise you will be spreading the organism back onto your mare.