Bottling after temperature drop / add more yeast?

Wondering if I need to add some dry US-05 to the bottling bucket on this one. I've never had to do this yet, but last night the ambient temps dropped to 64 from 75.

This is a Pumpkin Spice Ale with wlp002 that has been in primary for 3 weeks. I fermented at 67–68 in a water bath and pulled it out after 2 weeks to free up the water bath for two more batches. The last week it's been in ambient temps of 70–75.

I was going to bottle yesterday at 75, and made the priming sugar based on 75 temps, but it got put off and I'm planning to bottle today. Last night, though, I left the window open and the temps dropped to 64 this morning. This is a highly flocculent yeast so I'm wondering if I need to add some dry to the bottling bucket, or should there still be enough yeast in suspension to bottle condition. Maybe I'll even get a slightly clearer beer?

If adding dry to the bucket, I would probably do 1/3 to 1/2 packet. Would I want to rehydrate it first?

You most certainly do not need to add more yeast. First of all, three weeks is not long enough time to be worried about lacking yeast for carbonation. Second, 64*F isn't really that cold... it's just 1*F below the lower-range of optimal temperature of WLP002. Even seemingly crystal clear beer can still have thousands of yeast cells per milliliter.

I've had proper carbonation on a beer that spent two months in primary without adding more yeast and that one even got a cold crash for a week. You'll be fine