Not to worry, at least not too much. Wet cells are much more forgiving then their maintenance free brethren. Charging at the Gel settings will do less damage to the wet cells then the other way around.
If you equalize your wet cells every two months or so it will help reverse the sulfation that will occur with the undercharge. You will need a separate charger for that, maybe even one of those (dare I say it) portable cheepies from Wallyworld. As long as it will bring the wet cells up to their equalize voltage that should be good enough. Be sure to disconnect the wet cells from the Gel when doing this.
There are two types of fools...
One says this is old, and therefore good..
The other says this is new, and therefore better...