The electron spin polarization at the spin transition of the fractional quantum Hall effect was measured by combining Resistance Detected (RD) NMR with conventional NMR for small and large currents. The simultaneous observation of an unshifted and a Knight-shifted line is evidence of the different polarisation in different domain regions. Domains with full, partial or no polarization were also uncovered at v = 3/5 and 4/7. Surprisingly, measuring the conductivity with surface acoustic waves does not show any indication of the transition. This can be explained if the (conducting) domain walls have widths of less than 1% of the domains themselves.