The general consensus seems to be that the paper was hard this year. This means that the pass mark will be lower.
Although I've heard people talk about needing 65 out of 80 to pass, this isn't actually the case.
What they do is standardise the score based on the average score for all entrants, so although the standardised pass mark remains the same every year, this can actually map onto a different test score. The raw pass mark differs for different age groups too.
So even if the second test is also hard, it shouldn't be anything to worry about for those who have been doing well in practice tests and who performed to their usual levels.