When to start blasting 600mh from seed/clones?

When is a good date to start vegging under 600mh?

I currently have them under 50% so using about 300w mh. They are about 12~14 inches away from the seedings.
I have a 250 mh that i have clones under about 18~20 inches away.

My question is when is a good time to bring all those into 600mh ?

Can they start taking it after 2 weeks?

So simple question is when do i raise the wattage for vegging? After what week is ideal?

Thanks!

I think they're a little too close now. I'd back it off another 6 inches or more. As soon as you think the plant has a substantial root system, you can bring them back down to about 18 inches or so and give it all the light you want as long as the temp. stays right. You don't want the plant to outgrow what the roots can sustain. You really don't even need the MH to get them to pop up. I'd give it a week to 10 days.