Definitely no to the water. Sounds plenty to me. My girl has anywhere betweeen 2.5-4oz formula at every feed and she’s growing just fine
Mine is combi fed too and has around 2.5- 3oz formula, maybe 4 on a good day and BF inbetween feeds. But same as above, she's growing very well so I don't stress about volumes x
I don't think they're allowed water until 6 months, as it can lead to water intoxication.