Yes, both are possible. Milk pH ranges from 6.2 - 7.2, depending on season, species, age of milk, etc. Store bought milk tends to be more around 6.4-6.8. And yes, the amount of citric acid also drastically affects pH. You need a very narrow band for mozz, around 5.1-5.3. If your citric acid has picked up moisture, or has slightly lower purity or dissolution rate, then your measurement is off.
That's why I don't like citric acid for mozz in home environments without a pH meter. If you use a meso or thermo starter, you can always lower pH by waiting until it spins, but what do you do with a directly acidified curd?