Its A Learning curve

Hi folks,
Im 5 weeks into flowering im using for the first time the autopot system with smart valve (gravity fed )
Under a 600 watt hps in coco
They done really well in veg and started of alright in early flowering.
Until i came to find that 1 of the plants had turned completly bright yellow but it still seems to have buds the same size as the others. (which arnt as big as i expected).
The buds seem to have locked up and my head has almost been exploding trying to find out why.
After days of worrying and stress i think i have found the answer.

In the room i have put a new radiator to keep temps up and it it on a thermostat and is plugged into a extension lead.
Both the rad and the extension lead have a small round red light that comes on when they are working ie when it should be completly fu##ing dark these things are lighting the room up like little beacons, causing my girls to stress.

Does anybody else agree ???

No. no one else agrees. All of one plant is bright yellow, do you know what strain it is? Maybe it needs less nutes than the others or maybe it needs more nutes than the others?
You will have to stress for a while longer, its about a 2 year curve.lol VV

The strain is Black Domina

Of course, one I am not familiar with, maybe someone else is. VV