inverter ??'s

Why were they dry to beging with?
Well fast charging gasses them What is fast?
A pair of GC-2 are 220 amp horus give or take, anyting over 66 amps is FAST charging, even less may be (When I had a pair of GC-2 and an 80 amp converter I had to water 'em every spring.. I still have the inverter, still have a pair of 230 amp hour GC-2. plus some additional capaity, now water 'em every few years (2 months shy of 4)

also equalization charge will gas 'em a bit.
You might limit your charge current to 20% C/20 capacity

This will REDUCE gassing (boiling off of water)

Now, next, the fan
Thermostat controlled may run even when converter/charger or Inverter OFF.

I've had the SUN fire up the fan on my converter many times.

Since you have an issue with new batteries... put a voltmeter on them. Best not to blindly trust the existing equipment.

If you changed from AGM to flooded batteries there might be a charging profile setting that should be updated.

Thanks guys, it is an INverter & does make nice 120 volts. It ia a heart interface.
Guess I should have watched the batts closer, but I've never had an overcharging problem in all these years. This is my 3rd or 4th new set of batts. Charging them now, but I'm sure they are not as good as new. I'm monitoring the water usage as they charge. Hope I didn't mess up inverter too.

Please post the inverter make and model number.
Fill the batteries to cover the plates and charge 24 hours.
Measure the battery voltage with an actual meter.
Post the results.

First of all its a converter not inverter. Inverter changes 12vdc to 120 vac. The converter changes 120vac to 12vdc so you batteries can charge. When plugged into shore power for extended periods it tend to "boil out" the water in the batteries allot sooner. I turn off the breaker for the converter occasionally when plugged into shore power to aviod damaging the batteries. Normall the batteries will charge in a few hours. Yours could be damaged though. If they wont hold a charge they are toast.

The op could have a Heart interface inverter charger combo
In that trade winds

He didn't say

As for recharge, several days too full top off
But they are probably damaged, and will not regain full capacity, and will need replacement before the should have

No offense, but unless there are health issues, or terribly inclement weather
Checking new batteries is a must do item every month for several months after install, until you get a feel for their needs, putting off cleaning the fans may have caused heat damage to the inverter-charger, you may have caused yourself much more expense, time and battery performance will tell

Discharging and re-charging the batts causes water loss. If you use them hard, you need to check them often.

Do you mean INverter or CONverter?
INverters make higher voltage thanmtheir input. CONverters make lower voltage.
On an RV as old as yours I would definitely spend a few,dollars and buy a new CONverter, one with smart charge technology. The old CONverter you have is probably at best a two stage unit and is boiling the batteries dry