Charger and battery question

[mdav]

Let me see if i can explain this correctly. Charging my cart after use overnight quiq charger has fault code of two flashing red lights meaning less than .5 volts per cell. I have a digital readout for pack voltage it read 50.5. I checked each individual battery and after 10-12 hour rest four of the six 8 volt batteries are reading 8.49 8.5 range but two are at 8.36. They were the last two in line from the charger so i swapped them around and made my negative battery my positive and so forth. Charged again same result. I’ve ran the cart to about 80% then charged again and waiting for the results what am i missing or need to check? Sorry for the long post.