Do I have battery sulphation?

Greetings, I am new to this forum. I live off grid with a 4.8k solar array and a 840 amp hour FLA battery bank @ 24 volts nominal. I use a Trimetric battery monitor. We only use 12% of our battery bank's capacity on a daily basis. The Specific Gravity is uniform across all the cells. I use a calibrated refractometer. The specific gravity at the end of the charge cycle and tested when in float is 1.290
The batteries are behaving normally. However I can see something growing on the plates. It is grey in color and looks like fuzz. When I probe it with a stir stick the grey fuzz breaks up and goes back into the electrolyte and turns the electrolyte a cloudy grey color. All the sulphation I have seen in the past was white. How could this grey stuff be sulphation if the specific gravity is 1.290? I have really babied these batteries and have come to a full charge within 3 days and never lower that 85% SOC. The batteries are 4 years and 2 months old. There are eight UL 16HC interstate batteries. Any insight on this mystery would be very appreciated.
The batteries are behaving normally. However I can see something growing on the plates. It is grey in color and looks like fuzz. When I probe it with a stir stick the grey fuzz breaks up and goes back into the electrolyte and turns the electrolyte a cloudy grey color. All the sulphation I have seen in the past was white. How could this grey stuff be sulphation if the specific gravity is 1.290? I have really babied these batteries and have come to a full charge within 3 days and never lower that 85% SOC. The batteries are 4 years and 2 months old. There are eight UL 16HC interstate batteries. Any insight on this mystery would be very appreciated.
Comments
FWIW, Vic
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
High quality Deep Cycle batteries often have enveloped (usually only the positive) plates. This is a micro-porous plastic envelope that surrounds the plate and is usually heat-sealed shut. This does help reduce the effects of shed plate material causing discharge paths, either at the bottom of the cells, or, at the top.
Some batteries have a plastic plate, with some holes in it (often called the Moss Guard), which should also help reduce the chance of debris causing discharge paths between the plates.
The more time spent in Gassing stages the more plate material that will be shed (generally).
Also, there is still some plate erosion during Float. SO, IMO, it is best to try to set a Float voltage what will just barely keep a fully-charged battery, fully charged, at least on FLAs.
Just more opinions, FWIW, Vic
The batteries are running cooler and I am using less water. It seems the space between shedding plate material and sulfation is very small.
I heard one say its like dancing on the head of a pin.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.