Frisky Shelties after season has ended

I have a 4yo and 1.5 yo girls who have synced up their seasons. Just before their season and during, they were very frisky with each other which I understand because of the pheromones they were both producing. However they finished their season at least 6 weeks ago and they’ve started getting frisky with each other again. The 4 yo is urinating frequently again to like she does during her season. Could she be pregnant or is this normal or is there something else I need to be aware of?
Both happy and healthy in every other way (sometimes a bit too happy!)

Thanks in advance, fellow Sheltie Moms!