Ray,
I wait until the first true leaves appear to transplant into bigger pots, and sometimes not even then.If the seedling looks happy and is growing, I leave it in the original starter pot, and start fertilizing. I don't use grow lights, just a sunny window, and a lot of my seedlings get leggy. I don't worry--just plant them up to the first set of true leaves when they go into the garden. Think of long stems as potential root area!

I was hoping for advice in between.

Ok, in truth, you can transplant them when ever you want to. It's just easier and safer to do once they have true leaves so that is the usual recommendation. This is because if you happen to damage a leaf in the process the plant can grow more (it can't replace damaged cotyledons). If I have a couple of sprouts that happen to get leggy I transplant them DEEP regardless of the number of leaves they may or may not have - just take more care with them.

I will add that overcrowding contributes to legginess and 3-4 per pellet is overcrowded. And since they are in netted pellets you do need to remove the netting before the roots become entangled in them and make them even harder to separate. So, you might as well transplant them now.

Window use depends on the size, quality, and placement of your window. Not all windows are equal. ;) Using a fluorescent light set-up is one way of equalizing and improving the odds. Now Marlingardener has good luck with his/her window but most do not. And I think most of us don't find leggy seedlings to be as healthy or as productive in the long run so not acceptable. I KNOW that professional growers don't find them to be acceptable. But each of us has to decide for ourselves what is acceptable to us.

Bottom line - if it was me - I'd get rid of the netting, separate them and transplant them now and then get them back under the lights.

Dave