Cryptocurrency exchanges typically all show slightly different prices as they are usually not connected and their liquidity is sourced from different points.
So what you are seeing is not so much of a "timing" or "delay" issue, but simply natural differences across crypto exchanges.
Its worth noting that if the buy prices are lower, it typically means the sell prices are also lower, so having an exchange with a lower rate may seem good now, but if/when it comes to selling, you'll likely get less!
That's why Swyftx typically finds itself placed in the middle, we have the highest liquidity of all Australian exchanges and the lowest spreads, which means you always get the "Best" prices.
Ultimately when considering which exchange to buy or sell too, make sure to consider the trade fees and spreads as well as the market price in your final calculation.