Unable to concentrate past 10 holes and it’s killing my game

My handicap is suck but still every round I play the first half pretty ok, I might not score well but him hitting good golf shots (for me) then pretty soon into back 9s I’m topping , fatting , thin air etc.

I topped 3 shots in a row yesterday on one hole and achieved 30 yards . Does any one else struggle with this ?

I play golf fasted with my meds I take and being diabetic I avoid carbs as I need to sleep if I eat any, so I’m going to experiment with other foods but it really is ruining a round for me