In the winter in Vermont. I have had my temp. lower then that quite a few times before I got a really nice setup. Like 10 years ago. That's not cold enough to hurt the plant. But your right on the edge with heat. Actually I have grown some really nice stuff with those temperature changes. I know its not ideal though, but it happens. It looks like your NPK ratio is off. Go with lower N high P. You have a P def. As far as I can see. Its just starting so you can get ahead of this. But I don't know all the details. Looks like Nitrogen is high in soil. I bet the tips will show burning in a week. But that can be fix with doing what I say. But I'm sure I will get some rude comments on my opinions, but all well.