For this answer, and I'm sure others, I copied the english translation from the iTalmud app. Should I cite it at the bottom of the quote?
There are three reasons that I do (and advocate) this practice:
All translations embed assumptions and interpretations, and it's important to acknowledge this fact and that the translation you're reading represents a particular take on the text.
If the translation was by me, I want to make it clear that the translation you're reading is no more reliable than the rest of the answer (really a specical case of the previous reason).
If the work of translation was done by someone else, it makes sense to give due credit for that work. As it says in Avot 6:6, "One who says something in the name of its speaker brings redemption to the world ..."
As precedent for this practice, I'll point out that the MLA recommendation for citing the Bible includes "In your first parenthetical citation, you want to make clear which Bible you're using (and underline or italicize the title), as each version varies in its translation ..."
Whenever I quote the Soncino, I make a note of it. See here for one example: Shimi Ben Geira was Shlomo's Teacher?
I also link to the translation.