That tells us he does go down lower and that he is not just surfing along. So, when you do shoot, a midcycle number will be important to get, whenever you can - to be sure he doesn't go too low. That is a huge drop in 7 hours - from 400 to 70s. Do you feed him around +4 and then +6? That might even out the sharp drop. That can't feel good for him.
I'd get maybe a +8/9 to see if he is headed up and then of course +12 to see if he is over 200 and shootable.