i thought thats exactly what happen. jesse kind of told him "i know it was you" without really telling him and gus picked up on it and smelled something fishy. kind of like when walt told gus "i would never ask you that" when walt thought gus k!lled the kid
yeah, Jesse essentially made Gus come to the hospital just to tell him the kid was poisoned. That's fishy as hell. and honestly Gus' reaction has me second guessing that he was involved. I think Gus was legit trying to look out for Jesse by offering his a.ssistance.
I'm on my Mr Fantastic sh*t but I think Walt used Brock as a plant(call back to the gun landing on the plant pot) to get Jesse back on his side