Seems like that venue is very temperamental these days. Our club comp was held there beginning of Feb, and the fish were caught at distances just past their keepnets. Not sure what's going on there. I know the past weekend some good bags of fish came out at the Vaaldam.
Maybe the water is very shallow 250m into the bay? And with the hot weather, the fish moved to deeper waters, as the water could be to warm for them?? Just thinkin of a cause for your problem.