It's possible. 1 tablet per 20 gallons is the usual amount for treating chlorine and chloramines. The boil should have driven off most of the excess, I would think, but any that remained would make reproduction much more difficult for your yeast. If they never reached a sufficiently high population, it's possible they could have flocced out early, I suppose. Good luck with this brew, but next time, make sure to use it in the proper amount.