It's time to take those lids off. The lids stay on only until the seeds sprout, then you should remove them. What you heard is correct, keeping the lids on promotes dead plants. The plants need proper air circulation moving around them and no water on the foliage - only water the roots. They look healthy enough, just treat them as ordinary plants.

These are not my plants its just a library photo i took the lids off today as they were heavily condensated maybe i should put them back on again?. The article i read seemed to suggest you should not cover the seeds at all

In my experience, covering speeds seed germination, and increases the percentage of seeds that germinate, especially in small seeds, and those that need light to sprout. On the down side, keeping the new seedlings covered for more than a few hours softens and "stretches" them, making it difficult for them to survive the cold, cruel world in the garden. I would either not cover, or remove the cover as soon as little nubs showed. One other problem: even before sprouting, covers do encourage the growth of harmful fungi that can eat both seeds and seedlings. Better to mist the seedbed twice a day to keep the soil surface from drying out.

I have larger container and this cold weather left the lids off in the day then in the morning took them off and allowed them to drain snd dry read for lster, on bitter night in the gh (no heat) I'd cover in bubble plastic
Once they grew larger I'd not put lids on at all but using anything to hand created a tent effect with bubble if freezing nights forecast.....

These days I tend to buy plants fron the local nursery......they have the hassle ?

Some propagators have ventilation slots in the lid that you can open or close, which is a good in between solution while the seedlings at still tiny and need keeping rather warmer than the room they're in. You can open them during the day and shut them down at night which seems to work well.

I tend to leave mine on until germination. Then I remove them during the day to let max. Light and air to the seedlings, replacing them at night for a bit of extra warmth.

I have had 2 containers germinate well so ive removed the lids but wondering if i keep them still on the propagater? now they have germinated. Not sure if they should stay on the unit or not? haven't really tried the vents. I notice the containers do dry out quickly and need spraying with water everyday maybe i should switch the propagator off during the day but i need the heat for the others that haven't germinated yet especially the ridofolia need heat had trouble with these before with very late germination and they like heat.

The plants that have germinated don't need the propagator anymore. It has served its purpose. It might be time to "pot up" the plants that have germinated. Transplant them to a slightly larger pot with more soil. Then they won't dry out so fast. Do same for other plants once they get 2 or 3 sets of leaves.

Yeah, once germination has happened, take your trays out of the propagator and then if its cold at night you can always pop a lid over the seedlings. Now you've a space to sow more seed in the propagator! :)