I'm not saying you're wrong here, because they're probably just being asshole landlords (but I'm repeating myself). I'm simply questioning the timing aspect. If you suspect discrimination, document everything you've got and send it to a lawyer - perhaps there's a pattern.

That said, without a ton of evidence, it's a hard case to prove. Look at ol Don Trump back in the 60s and 70s - they basically had to prove by his own sheer malice and stupidity that he was guilty of it. They literally found applications with a big C written on them for "colored" to show a pattern of discrimination against black people.