Potted the plants up in final pots mid week and removed the smallest plant from the grow.
Had trouble with temps dropping to below 15c this week and had PH levels going up to 7, both all sorted now and look to be growing well since making adjustments.
@Waters, All is not lost, just been to trim the fan leaves and checked all plants buds and no signs of rot anywhere else. so far only thing lost is the top part of the main cola on one plant, had to cut off the top 6 inch ๐ข fingers crossed it doesn't reappear ๐
@Pigeonfeed01, Yeah looks to be an odd phenotype issue, had the blurple leds off yesterday to have a look at them under white light and the runt is a lot darker shade of green compared to the other 3! it's flowering now though so will have to wait and see how it smokes ๐