Yup- when trying a new product, 'less is more'.
Mix up your fert solution. Check pH. Add about a half mL. Check pH again. Repeat until you get to where you are going.
Vinegar is not as bad as you think. It's a perfectly serviceable emergency backup for soil growers. Hydro, not so much!
If you use a humus-based compost, you will have a much bigger range in which to err before pH becomes a problem- it's buffered by the organic acids. Organic growers should be aware of this and learn to use it to their advantage.