The implication of those words was quite heavy: the Divine Doctor is my good friend. If there's something wrong with your brain, the Divine Doctor will know upon examination. The deeper meaning is that if you don't listen, even if there's nothing wrong with your brain, the Divine Doctor could find something.
Both Prince Qing and Prince He were old and experienced. They knew very well that the Emperor's mind was actually fine, and as for the poison, it must have been completely cured. It's just that Prince Zhuang didn't want the old man to return to the throne, so he was in cahoots with Ye Zi'an.
They had no objection to whoever was Emperor as long as it was someone from the Baili Family.
