Still having issues with emmissions after replacing O2 sensors for P0135 code.

Question

Followed the information that Reynaldo gave me and found O2 sensor in question to original problem was black at the base. (question from 5 days ago) The other two sensors looked normal with tan oxidation, but replaced all three O2 sensors since the vehicle has 95000 miles and the sensors were not that expensive. Reset the codes drove about 10 miles and now I am still getting a yellow caution code on emissions. No code is setting after driving another 20 miles. What I am seeing on the recorded live read out is a constant reading of 99 on the short term fuel trim (B1-S2) vs -7 to +7 on STFT on (B2S1) and (B1S1). What would cause this problem?