I've been told by others,that here in California,they do that in winter. Then,return to normal when summer gets going.

They don't do that in New Jersey when grown under florescent light in the basement. So...I don't know if it temp related or light related or something else (e.g., soil, drainage, etc.) Yes, do they have a very slight yellow hue, but not like that, normally.

I will post a pic of mine on the weekend.

Mine did that when they got sunburn...

First, it looks like you may have planted it too deep. Don't dig it up, but move some of those river rocks back.

Second, try some fertilizer.

Here's what they will grow into. These went in the ground in 1998 from 7-gallon nursery cans. Two Spindles and a Bottle in the middle.

Mine did that when they got sunburn...

fawnridge, Those are just beautiful !!
~SJN