Lovely pink hearts, but etoliated

I have this string of hearts under Barrina T5 lights (about 20cm away). I got the lights because I felt like it was getting more etoliated even in summer in the window with the most light, and it had lost all the pink.

Now it's beautifully pink, but there's no change in etoliation of the new growth – you can see how close the leaves are at the top of the pot (when I got it) versus now.

What do I need to do to get the leaf spacing back to how it initially was? Surely it can't need more light – according to a light meter app it's about 7000 lux at the lowest point on the plant and 14000 in the pot itself.

Any advice welcome, thank you.