For the fert. it depends. Did you amend the soil with manure or anything else yet? If it is just straight garden soil I would start with the 8-5-0, IMHO. Just to start. That way you're just promoting root and veg growth. If you get a warm front the plants are less likely to head too soon with less K. If there's manure in there or you need to side dress a little later, I'd use the 4-4-4 or 5-7-3 then. As you know, the heads are huge clusters of tiny unopened flowers, so you want a higher K value closer to harvest time than you would with lettuce or cabbage, which you really don't want budding at all.
That is just my opinion, though. Others will have different opinions. I try to fertilize my plants based on what I expect from that particular plant at that particular time. Seems to work out pretty well. Better with some plants than others.
They look really good! I wish it wasn't too hot for broccoli and cauli here! Do you wait to harvest the purple sprouting until the flowers open? Or is it just called that because the sprouts are purple?Would I be wrong in assuming the heads are purple? I'm planning a purple themed garden for the fall.