hi there jimbob17 looks like you might have had a few slugs too, they might be what caused the marks on your broccoli stems (I can't really see the stems on the photo). If your unlucky it could be a Pathogen, bacterial or fungal.Check out some photos online of Black rot, black leg, black leaf spot and grey leaf spot. If canola is grown near you the likelyhood of these diseases rises significantly. If you don't like what you see, pull up your brassicas and bag them, at the first opportunity burn or tip them. Don't plant them in that spot again for a min of 3 years There are however a number of less sinister possibilities, the aforementioned slugs, with yellowing caused by nutrient deficiency. Do a ph test (kits are usually available at nurseries and produce stores), to grow brassicas you need a sweet soil - ph 6.5 to 7. Another cause of deficiency is water logging so check your drainage (dig a hole fill it with water and see how long it takes to empty, ideally less than an hour in a vegie garden) if drainage is slow build up your beds and NEVER EVER walk on them when their damp. Sometimes broccoli just seems to get tired and lanky you could try cutting off all the old leaves and stems and side dressing with dynamic lifter or blood and bone, or some rotted manure. I"ve had some born again broccoli after this treatment. Be sure to practice crop rotation waiting a few years before you plant any brassica family crops in this spot again.
all the best
janeymax