I've used wet cell with gel for 1.5 years in a pinch. All seemed fine when I returned to the states.
Technically not good to charge a gel at wet cell charging
voltages. Maybe check your charging
voltage with a Volt Ohm Meter.... or many instruments have a voltage meter built in. See what you are running.
How is your battery switching set up? Do both charge automatically? or do you switch to charge each bank?
So many questions.....