To be honest, I won't add any acid to any wine without first testing it, if you don't have any way of testing the must - taste it.
I usually make any adjustments prior to fermentation, but if you don't have any way of testing the must use your taste buds:
If the must tastes good, I'd wait, the acidity in strawberries comes mainly from citric acid which comprises about 88% of the acid content - I wouldn't add an acid blend, you don't need tartaric or malic acid in your strawberry wine.
I make a berry wine that everyone seems to really enjoy, everyone has been asking for it - I use strawberries, blueberries and raspberries, I tasted the must before fermentation, I was surprised that there was absolutely no acidity to the wine, it tasted really sweet; I went looking for my citric acid but thank God that I couldn't find any....after the wine started to ferment and breakdown the berries, the natural acidity in the fruit came through and I was surprised at how acidic the wine became!
Wait until the wine starts fermenting, taste the wine, if you feel that you still need to add acid to the wine, you may want to add the acid in steps, maybe add half once fermentation gets underway, taste again the following day and add the rest if you still need to.
I hope that this helps.