There’s two different types of price collusion, and only one is illegal. The first is using public signals (ie looking at competitors prices) and setting yours to match. This is perfectly acceptable, and is usually unspokenly enforced by tit-for-tat strategies.

The second is when you get together and say, “1bd studios are $1200, agreed?” This explicit coordination is illegal. IANAL, but this looks closer to the second.