My brassicas have cream coloured blotches on them. As far as I can see it's not caused by
insects. Could it be some sort of deficiency ? any ideas?
I have seen it before, particularly on newly planted brassicas. I've put it down to sun scorch while the plants are settling in.
If it is happening on older established plants then I'm at a loss like you, But it sounds more like a physycal problem rather than a nutrient/pest one.
Let's hope they grow out of it. ;)
I can't think of a brassica that ever does look happy just after transplanting... even if you have perfect soil, perfect conditions and are planting from perfectly timed pots (rather than bare roots) they always contrive to look like they're struggling with your desperately bad husbandry.... that said they soon perk up again afterwards... AS my dad used to say .... "They lie like Labradors".....