There should be five bottles in the minefield, although they are hard to see and I usually stop after finding the three that Akim wants. The best way to find them is to criss-cross the minefield while holding down your "Use" key. The item text should highlight when you get close.
A mine detector will beep when you are near a mine, but it doesn't really tell you where it is. You can see and avoid the mines much more easily at night.
If you still can't find the medicines, try turning your grass density to minimum (Options - Video - Advanced - Grass Density.) Remember roughly where the slider was before you do this, so you can put it back afterward. Setting it too high can really affect your frame rate!
Last resort if you still can't find them...