Barb
Spear pull can and often does happen soon after cold a lot of times when it happens later it can be to much moisture before plants have turned the corner out of winter.
Last spring my Washys made it through winter (barely) but the spear didn't pull until late May.This was because of a wet spring.
My Trachys pulled within 2 weeks of cold weather.Not sure if it was below(mostly)freezing temps for 3-4 days or 12(F) absolute low.
My guess would be the former,that's what you get for treating your first years like your more established palms
If that is a current pic of your Naini Tal I'm sure it's fine(Rostrata too)and I would guess they have not seen temps that cold in their enclosures,your potection is so close to the ground
and so well insulated,I doubt they have seen cold like there was outside.
You Naini Tal would look all shriveled up if it had seen -5(F) and the leaves would be closed up