For future reference, for reference of other newbees and for possible discussion:
"Citric acid added to a must before fermentation will largely be lost during fermentation. Thus, it is best to add it after all signs of fermentation have disappeared. Malic acid can be added anytime, but it too has a potential disadvantage. Malic acid buffers to a fairly high pH, so it should not be used if the intent is to increase acidity and / or lower the pH. In the latter case, tartaric acid is the additive of choice."
http://winemaking.jackkeller.net/acid.asp
So adding citric acid during a ferment is bad since much of it might be lost during the ferment anyway. You'd just be giving your yeast a hard time for no good reason. Since this was added towards the end of ferment it should be ok. Btw lemons have some sugar in them so this might extend the ferment just a little. Shouldn't have much effect here but it's possible that a ferment picks back up if you add lemons to secondary before stabilizing.
EDIT: It seems citric acid could increase or decrease during ferment depending on yeast strain according to Medsen Fey in this thread here:
http://www.gotmead.com/forum/showthread.php/20366-Acid-Metabolism-During-Fermentation
Medsen was a well knowledged contributor back in the day. one of the best we've had so that post's credibility is rather high. Wish I had more info on this subject. Anyway, unless reduction of citric is rare don't add citric acid before fermentation just in case the strain you use happens to metabolize citric