I made a few batches of wine from various frozen concentrates before I
had an acid test kit.

They are all young (under 4 months) but when I thieve samples they all
have a tartness to them that I'm wondering is because of age or the
acid level.

I added 1tsp of acid blend to each of them before fermentation without
any testing....is it too late to check and adjust the acidity of these
batches? They are in various stages but all are done fermenting and
have been stabilized and or fined. They are Welches white grape, white
grape peach, Old Orchard apple/passion/mango, and apple/cherry. I
don't know how standard the acid levels on these concentrates is and if
some of you can tell me if 1tsp. of acid blend is "ok" here.

This tartness is the kind that gives you a little pucker and feel in
your jaw.
I did notice on the oldest batch that the tartness is fading so perhaps
in 6-12 months it may be gone but the batch I just tasted after racking
(2 months old) has got some pucker power to it. I'm not experienced
enough to know how much of this is "normal" for young wines or it it's
a problem and if I can adjust it now or it has to be done before
fermentation.

John F