Brussels Sprouts are a very long season crop... it's unlikely you can get enough growth to produce sprouts trying for a fall crop... figure a minimum of 100 days from transplanting... and start seeds 6 weeks before that.
But fairly early varieties of the rest could be started now, then transplanted (with some sort of mulch to help shade the soil from the late summer sun) in mid July.
I found a variety of broccoli called Coronado Crown that is incredible... I've gotten 16" diameter heads from it! I think it was from Park Seeds, but not sure.
Johnny's Seeds has a variety of cauliflower called Early Snow. It's VERY early... 45 days from transplanting in Spring. Fall planting always takes longer, as day length shortens, so keep that in mind.
Cabbage is personal choice, but again, you need to find a shorter season variety. We grow early types (red and green) for fresh summer eating, and then long season keepers for putting in the root cellar.
Most greenhouses around here simply use the cheapest seed, which means open pollinated varieties, or, in the case of tomatoes, older hybrids with "name recognition". Again, for folks without growing issues, they provide acceptable production. But if you are having problems, hybrid vigor really can make a difference. Plus, you can find hybrids with disease resistance... Google cabbage diseases and see if clubroot (or maybe cabbage yellows, although it doesn't really sound like it) sounds like your problem. Then consider finding seed for next year for resistant varieties.
Even if you aren't set up to start seeds indoors, direct seeding your Cole crops will give you a better chance of a crop than transplanting varieties which succumb to disease mid-season.
Summerthyme