Can you post a photo of the lemon chicks with a regular buff chick?
I have on a couple of occasions hatched a chick that was pale yellow, and the initial feathering looked pale yellow, but in final feathering the bird was white. Not sure what caused that.
I know that cream silkies have been achieved, although not in any numbers. If both parents are buff, then a further diluter must be recessive and carried by both parents, otherwise it would show in whichever parent has it.
Buff plus lavlav gives isabel. Buff plus igig should give either cream or lemon. I can't think of any other recessive red/gold dilution genes other than silver, and they wouldn't be buff if they were silver. Although males could be mixed Ss, golden.