The whole point of the AGM (absorbed glass mat) type is to have just enough electrolyte to wet the mats between the plates. This way it cannot spill as the mat holds all the electrolyte. If you added water, you converted it to a wet cell battery and further, diluted (reduced) the acid strength that the manufacturer designed it to have.
Don't be surprised to have a weaker, lower capacity battery and one with a shortened useful life. They are "sealed" to keep owners out of there and from meddling with the technology. If you had a warranty, it should rightly be voided.