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It could be that they are not getting enough air

At first glance it looks like a low water / high heat situation.

Which diary is this from? That would help us to better advise!

The problem is that it's at full blast all day and 3 or 4 hours before the lights go out, it gets like this.....

looks thirsty to me

Looks like overwatering. Simply let her dry out the hearth and then water just the outside of the soil

It's either nitrogen toxicity or to much watering or simply both. If you know for a fact your not over watering then it's most likely nitrogen toxicity witch locks out all other supplements the plant needs