I would nip off offending leaves and give a good feed.
It's showing on 90-95% of the leaves on all but 1 plant, it appeared and spread very quickly. I don't think defoliating would help. If it is Septoria Leaf Spot it looks pretty much terminal, although all the info I can find is from the states, if it was an issue here I'd have expected lots of uk based hits.
It's not as if the environmental conditions have been right for it and having replaced most of the glass this year the greenhouse was spotless and the compost was new.
The plants are well fed with comfrey and had a epsom salts last week as there was a little mg deficiency in the older leaves. The tomatoes in the top gh appear to be fine - so far.
