So, not sure anyone mentioned this before, I got it from motorsport.com
Verstappen:"I don't think it's because the Honda engine came into the back [that Red Bull's chassis got worse]," he said. "It's just with the regulation changes, the front wing especially became a lot more basic.
"But we were really good at controlling everything that was happening with the front wing last year, and the year before. So they took a bit more of our strength away. We have to fine-tune around it.
"Maybe in the beginning of the season so far we have not optimised that, and we know that. We're trying to get back on top of it."
That makes sense, though I thought Mercedes also were very good, though in a different way perhaps, and they do not appear to have lost so much from it.