Using a renormalization group analysis for the tricritical behavior of dilute polymer solutions with many chemically different polymers, we show that the chemical. mismatch is indeed important. This is contrary to the irrelevance of chemical mismatch in good solutions. We find the second virial coefficients at the tricritical point to vanish with chain length L as L(-1/2)[ln(L/a)](-9/11), where a is the small cut-off. This behavior is in a different universality class from the one for the tricritical solutions of polymers of the same chemical type. The generalization to block copolymers is also addressed.