Petunia seedlings not growing

Lewisium

My petunia seedlings are in 9cm pots and have been under 16 hours of grow light for the last few days without any real signs of extra leaves or growth... Should I start a new batch and only use the grow lights for germination? Or should I keep the existing ones on a conservatory windowsill?

I had thought about putting them In a press seal bag and elastic band around the pot to create their own bio bubble..? 

Perki

how big were the seedling when they were transferred to 9cm pot ? A few days isn't very long give them a bit more time, grow lights are for plants which are growing .

With petunia I pot on into 12 cell tray and then into 7cm pots . Plants potted into a pot to large suffer and struggle to establish and usually site in wet/damp cold compost.

Lewisium

They were only very small, 4 small leaves. Should I leave them now or move them into celll packs?

They don't seem to be doing any growing under the grow lights now 

Nanny Beach

Not much help I  afraid,I can grow pretty much everything from seed, don't have experience of grow lights, but have always found petunia difficult to grow,buy regardless, yes you potted on too quickly

Kili

Just leave them under the grow lights. Petunia are very slow to get going. If you keep moving from one pot to another it will check their growth even further. Be patient they will slowly start to get bigger.

If you grow them next year sow them a month earlier if you want them at planting size early in the season or as you have now they will simply last later to the end of the season.