As is so often the case, I have seen 'Sally Holmes' with foliage disease problems on a few occasions, despite it usually being clean. I've even seen a little section of heavy rust infestation in the midst of an otherwise uninfested, huge stand of Rosa nutkana in Whatcom Co. Roses in pots seem to be particularly prone to bad leaves that they might not have in the ground, further supporting the idea that there is a nutrient deficiency connection with at least some fungus problems. And there is always the problem of leaf fungi occurring in multiple strains, so a clean plant here may not be there just for that reason alone (different strains of blackspot rust or mildew here than there). Saw a copy of new Phillips & Rix book BEST ROSES at Lynnwood Barnes & Noble today, they rate 'Mutabilis' 5F. Seems optimistic, they also rated True Musk (perhaps hardy to) -10F in same publication so they might've been on a roll. (Photo used for Rosa moschata not same one showing clearly correct plant used before, this time really looks like yet another shot of R. brunonii passing for it--based on the branch section shown, and not the whole plant).