That is strange if the others have been turning yellow all that time and not those. Sorry but a little yelow in the last few weeks is normal but yours started to yellow way too early. I have AK-47 beans but have not tried them yet. If anyone who has AK-47 might be able to help ?. I have grown Northernlight, orangebud, papaya,and some bagseed and none have yellowed until the last week if much then. How strong is your nutes, cause the the yellow looks like it starts from burn on green leaf tips ? Have you run another strain and this not happen ? Every strain is dif. What are your nutrients and what water are you using and any add ons like calmag+. Yellowing is the plant burning up or the lack of nutes and it's eating it's self. What kind of water do you use ? I see what you mean but the new ones are dark green like lots of nutes , maybe burning around the corner or they can take it. Let us know what your mix is it will help greatly.