Recover from tall seedlings

As everyone has already said, just move your light a bit closer/turn up the brightness a bit and take your cues from the plant if you can. Only thing I would add is what @FreddieSpaghetti alluded to - get a fan on her. The draft from the fan will make her lean over a bit initially (you can support her with stick if needed), but after a few days it will have strengthened that stem to the point that she doesn't need supports anymore. These things are resilient and will grow back stronger for it!

I find the best thing to do is spend some time listening to your plant. Seriously lol. Start increasing the intensity until your plant tells you it's enough. She'll stop reaching when she has enough light.

45cm.. 500 umol. So if your light is 1000ppfd aim for 40% then up it as your veg goes on. Never exceeding 75%.. Keep full % for pre flower When you get into the ripening stage. If your light is strong, i know you got a 200w infin. So, look up there ppfd chart. For ripening aim for 7-900 ppfd especially the last few days. Or if you like your bud super cloudy.. then the last wk or so. Again, all depends on the quality of your lights output. As for your seedlings. There's not much you can do. For now. As you can't repot putting them further below your pot line, (therefore shorting your stem from sub to coly, "leafs that 1st pop out" as the stem is so young. You risk damping off. After 2 weeks or so. When you got a green stem with some give. You can repot planting it deeper. But, as for the plant itself. No big deal.. She'll just have a big base stem.

What you want to do is let the plant tell you how much light she needs (not how much the light manufacturer tells you to give) ... and this lady needs more light. You can either bring your light closer or, if it's on a dimmer, turn the intensity up... honestly, I run my lights at 100% from seedling to harvest simply adjusting the height as my plants grow... Good luck!

io arriverei anche al 50% e aggiungerei un po' di terra per coprire il fusto ed evitare piegamenti

Looks spindly you can turn the light up to 35% or move them 2-3 inches closer.