Hi
I typically see a stretch from my plants over the first 1-3 weeks of flowering, and and a few other g.d.p diaries show a slow progression in stretching. So I wouldn't worry about it, watch it over the next couple weeks and see what happens. The plants look incredibly healthy and a 3 degree difference in temps shouldnt cause any big problems. Some plants won't even double in height, but they'll fill out width wise with dense buds.👍