I often see UPS batteries like that, it's not uncommon. Nothing to worry about, typically happens due to overheating / age and being lead acid batteries.
As for the Warranty, I very much doubt batteries would be covered unless under 12 months old, due to being classed as a consumable.
As for the Warranty, I very much doubt batteries would be covered unless under 12 months old, due to being classed as a consumable.