Reproduction AGM Battery Question

So my repop AGM yellow top Mopar battery is now almost 6 years old. It has worked well and have had to charge it a few times after long, mainly winter time storage. Always with the charger adjusted for AGM.

I have noticed a little discolor on the top in the last few years after charging. It wipes clean and the terminals are spotless., but! Being AGM can you add a tad “ounce or so” of distilled water in each cell to help it last a few more years? The caps do twist off.