ive also had the odd mutant in the past, but they usually sort themselves out after 4th or 5th node, i find once the plants gets bigger the problem sort of fades away, different strains repond different to temps, ive had several strains that show heat stress when others dont, when this happens i just move the plant with the problem to a corner of the grow room so its further away from the light then it sorts itself out, i know autos tend to suffer with heat stress more than regular plants, the auto northern lights and auto bubble both show signs of heat stress unless their further away from the plants, but then you need to think where ruderalis grows, it grows in pretty cool climate in mountains so growing it under regular temps is going to cause issues unless the breeder has worked with the strain to breed that trait out,
but as we all know each strain will have 2 or more pheno types so out of 10 seeds you could end up with 5 plants that suffer with heat or have a genetic issue and 5 that dont have any problems at all, if you look on the seed banks you will see some strains have 4 or 5 pheno types from the seeds.
different strains grow in different parts of the world, uk cheese is used to a more humid and cooler environment compared with a kush or flash type strain, so you will always get slight variances depending on the back ground of the strains, i bought a blue mystic about 18months ago and it was badly deformed and stopped growing and died at the 4th node, so i searched on the net and many other growers had the exact same issue, some on this site and some on other sites and the problem was with this one breeders seeds, so i had it replaced by the seed bank but with a different strain as they pulled it from sale, its back on sale now so i bought some a couple of weeks back so will try that strain again when i get room.
so just see how it does now the lights a bit higher, give it 48 hours and see how it looks, if its showing signs of looking better then it could be just down to heat stress, low humidity can also cause a similar problem if temps are to high as the plant uses more moisture than its taking in, i can only give you info i have picked up from my own experience and others will have different ideas and different cures,
check out the plant help guide in my sig below, it covers all types of plant problems so that may help you in future if you have anymore issues,