First ever grow and need help

So its my first ever attempt at growing and I've done fine so far, using fox farms soil and liquid fertilizers for veg and now flowering, havent had any issues till now, yesterday I noticed some lower leaves shriveling and dying on a side branch/small budsite, I didnt think much of it as I heard cannabis does this to leaves not getting much light and it's natural, however this morning I checked and noticed all the leaves up top are starting to curl and twist as well, I'm not sure why because the rest of the plant is healthy and not a single leaf on the rest of the plant is showing any signs of problems so it's hard for me, especially as a beginner to diagnose it, I would really appreciate some help

How are the temp and humidity conditions in your grow area? As I understand it, leaf tips will curl up trying to provide shade for its stomata if it's too hot.

Temps range from 69-73 from day and night, humidity is like 45% and no other branch or leaf is showing the same, which is what's really confusing me, if there was a problem wouldnt the whole plant have it?

I'm not exactly sure. Hopefully someone that's had first hand experience with leaf tips curling upwards will chime in with their remedy.