Hellebore black spot looks more like brown splodges. I've just pruned my new hellebore back as it had black spot and the flowers have already gone over. I'd be interested to know what these black dots are as my fatsia and one of my camellias have it. I put it down to stress from repotting but I have no idea tbh.
I've never heard of spider mites 😅 I guess your hellebore spent a fair bit of time in a greenhouse in the nursery. And fatsia is particularly prone to spider mites. I need to get out there and treat my fatsia and camellias with insecticide as I don't remember if I've done it this year yet.
I think the first sign is discolouration which looks like nutrient deficiency, then the black dots and then the webbing. You might not see webbing until much further along. I'm not sure if your dots are the same as mine, it looks the same though. I looked at the previous photo of your hellebores and there are some brown splodges that look like hellebore black spot as well.
@ublaszko Yes I agree with the black spot, I know we def get that and I remove and bin the leaves each year to try and help. I’ve removed all the leaves of his hellebore, in the hope that it will get rid of the mites :-)