To determine the ta, you need a acid titration kit. They run about $10 I think. They work pretty good, will give you an idea. I am guessing but it sounds to me like you acid is low with a ph that high. Adding acid blend will raise the acid but no knowing what it is keeps you from knowing how much to add.
If you are able to get a titration kit soon, I would do that and based on that I would add acid blend based on what winecalc shows you. It is free and indispensible.
Ok thanks. I got the two confused. Thought ph would tell the acidity. Too late for me to get the kit right now . I do have acid blend so I may add some to the must.