Is this calcium deficiency or heat burn?

[Ccfender4]

Strain: Pineapple Express
# plants: 4
Setup: indoor, 96 sq ft
Median: soil, 5 gal pots
Nutrients: fox farm, big bloom, tiger bloom, bat guano
Lights: (1) 315 watt lec's
Room temp: 75 - 79
RH: 50% - 55%
Ph: 6 - 7
Watering: as needed

Two of my plants are doing bad and I'm having difficulty identifying the problem. I am getting spots on the upper leaves and they are beginning to die. They are a dark brown color and curling upward. Is this a calcium or radiant heat problem?

 

[Ccfender4]

 

[2clean]

I'll flush because could b mute lock out. Looks like calcium but looks much worse. Make sure ph is on.
I seen bad soil cause that. Not enough drainage, poor quality etc.

 

[Ccfender4]

Wow, will flush asap. Hopfilly that will resolve my issue. I'll check the Ph too, thank u very much for your insight.

 

[2clean]

how is your soil,does it have good aeration??? how are u watering it.. sometimes root rot will look like that.