I agree with Sawa's comment, saying that consistency would require "先勝は午後が." Now, assuming that:
- We're talking about three things that we introduce: A, B, and C. It's thus normal to enumerate them using "は":
When you group everything in one sentence, you get
which is basically the structure of your sentence, except that you have "され(ています)" instead of "で(す)".
Without even thinking, just learn the patterns AはBが良い and AはBが良くない, meaning "B is good/bad for A".
We have three of them here; for example: "The afternoon isn't good for the
early winners''" (early winners'' being whatever translation you use for 先勝).
This pattern is exactly like "AはBが好きです" or "AはBがありません"。
The person doing the action in passive voice is indeed given by に. However, this actor can be implicit, as is the case now.
The sentences are of the form:
(it is understood that) afternoon is bad for early winners
where the subject of する is undefined, to make the statement generic, à la "it is said that."
I don't believe that it is the moment of the day that causes bad luck, it is just when bad luck strikes. Passive is just commenting how the three groups are classified (by you, me, or anything else, which is not explicit.)