Ako, Thanks for providing the Float and early Bulk SGs.
There is more variation in the SGs than I would have guessed. AND, for those measurements, it seems that your high SG situation, is not as extreme, as you noted before -- perhaps some of your changes to the charge parameters are helping (?),
If this were my battery bank, would try to discharge it deeper than normal -- to about 65-ish percent SOC. Watch the voltage on the second battery in the table (the one with the lowest SG cell), or the SG of that battery/cell during the discharge. Deep-cycle batteries DO like to be cycled relatively deeply, on occasion.
After this discharge, fully charge the bank, and EQ it in the lower range of the recommended EQ voltage, if possible with the TS-60. Would recommend trying to recharge the battery immediately after this discharge, as letting a fairly deeply-discharged battery sit, off-charge is not the best thing to do.
If you could try charging only that battery with a 6 V charger, that might be even better. If doing this, the output of that charger must not have its output connected to the safety ground, or either AC input connection ... am not certain where you are located, and the standards used for safety grounding, and weather the battery has a connection to any safety ground in your system. If you have a 6 V charger, you could quite possibly charge this lagging battery while the system is running in Float. This might be an adventure that you might not want to try.
FWIW, just some opinions, Vic