In looking at the particle charts I see 3 Sigma baryons with very similar masses and other similar properties, which makes sense since they all have one strange quark plus two others from the (up,down) group. As I understand things, up and down have similar small masses but differ in charge, so if you take a strange quark and two of the (up,down) group you can get 3 different particles similar in properties except for the charges from up/down - uus, uds, dds. So far so good.
However, there is also a Lambda-0, which is also uds, like the sigma-0. As far as I can tell, it is exactly the same as the sigma-0 (spin etc.) except it is less massive. (in fact sigma-0 decays to it). So what is going on here? What are the quarks doing differently, and what prevents them from doing the same to form a lambda-plus? (I assume the Fermi stats prevent two up quarks in such a thing, but if so, why can the sigma-plus exist?) What changes when the sigma-0 decays to lambda-0? Trying to find the answer results in adding and subtracting the quarks and multiplying by the square root of two - huh?
Possibly related question in reverse - Take a quark and an antiquark from the (up,down) group and you get three pions, plus, minus and 0. Plus and minus are understandable, u-dbar and d-ubar. But why not two pi-0 mesons? U-ubar and d-dbar? Again they are adding quarks and multiplying by the square root of 2 and voila, a pi-0! Huh again?