Yellowing leaves and brown spots.

Hello,

Can someone help me diagnose my sick plants please? The lower fans are getting some brown spots on the inner portion of the leaves, and then the leaves start to yellow. I'm leaning towards nutrient burn, or calcium deficiency. Would someone else be kind enough to help me try to pinpoint what is happening? Thanks in advance.

two things I will ask
1 are you over watering?
2 do you have drainage holes in the cup?

Drainage holes yes. I let them get quite dry before rewatering. I may be giving them a bit to much water when watering though.

It also got very hot in the room during some late August days.

Walterwhiter said:

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What he said. It looks like a nute burn to me.