the amount of chlorine in tap water is never a concern. you don't have to let it sit out 24h either. that is probably adding to risk of a problem more than solving anything. Cl is a trace element used by the plant. it needs a small amount anyway.
Does not look like pest-related.
If that showed up the day you brought it into the sun, light damage is definitely possible. Potassium often starts damaging the serated tips before anything else, but i'd wait to see progression before reacting with more K. Also, since that's mobile, it'd be odd that it started up near the top, but exactly where light damage would start.
i'd see how it progresses. Plant has a good green to it. It's not overfed or underfed that i can tell. some minor tip burn. Might be 1 element in soil that's a bit hot but not too bad.