Yellow leaves with brown spots in Flower

Day 37 Flower. Here's where I'm at currently. Not exactly pretty, but I've made some progress - and they are still alive!!! How far do you think I am from harvest?

I do most of my growing out back. This year it got down to the high 20’s for around 3 days. The highs were in the 50’s but cloudy. Some plants just slowly dried.
But one choc trip that was partly harvested. The buds took off. Turned purple is going brown like the color of milk chocolate. My starts are outside when it gets into the 60 mid April. I have to watch for snow and hail The weather is different here in that day night normally 20-30 degrees but last week in two days it was 72 degrees. I used to believe the books but I will test to see if it is true.

The reason I was reading this post is I have some sativas that drop fan leaves as the new set grows. Had it on 5 plants. I transplanted the 2 in veg but doesn’t seem to help. I use ocean forest and mix in some old stuff and perlite. I flushed one plant today see what happens. Can’t find my PPM meter.

I just saw your thread, this might be late, but anyway it could be helpful.

Quite a few things have been said:

1. Low night temp. 59 °F while not ideal, it will not produce the effects you were experiencing. What it will do is slow the rate of growth and promote stretching.

2. Calcium def. This element is immobile, which means the symptoms will be shown in the newer (top) leaves, not the older (bottom) ones like in your plants.

3. Phosphorous. This element will produce black / dark blue tips, edges and/or spots on leaves.

What it does look like (chlorosis with rust spots) is Potassium deficiency and with the rest of your foliage looking very light green too, there could be some Nitrogen def going on. Your plants looks hungry for some bloom feeding.

I would get an EC/PPM to check what nute strength you are using. Many cheap ones you can get.