Are Neons In Right Tank?

That could be a possibility.
From my experience, I've had penguin tetras in a tank with glass bloodfin tetras and hatchets. Since moving the glass bloodfins to a different tank, with lemon tetras, gold stripe corys, and a BN plec, they are much more outgoing and spend a lot more time in the mid-water areas and at the front of the tank.
My pengiun tetras can be a bit boisterous, but the black neon tetras that are currently in the tank with them seem to be taking it in their stride, but there are a lot more black neons than penguins in that tank, so perhaps that helps.
The hatchets remain fine in with the penguins, black neons, and my other BN.

How are your neons at feeding time? Do they hide away until the penguins have finished, or do they feed at the same time?

How many neons do you have, and how many rosy tetras and penguin tetras do you have in that tank? It might be that increasing the shoal size (and especially .v. the rosy and penguins) gives them more confidence.

Do the other fish use the open area of the tank or is it pretty empty? I imagine the penguins stay in the top half?

Another factor to take into consideration, in my experience, is the water flow. I've been changing filters around recently and where the fish hang out is entirely dependent on water outflow, with some species less bothered by being buffeted around and others preferring to be in the area of least flow.

Thanks for all the replies. Apologies for not replying sooner.
The neons seem to be coming out a little more. I don't have floating plants, but will take a look into again. The flow from the filter is at its most, could possibly turn it down slightly.
I do notice when lights are off the Rosys and Neons are always in the right hand corner under the filter. When lights are on the Rosys swim around the whole tank.
Both my tanks are in the corner of a bedroom, door on one wall, window on other and no kids, just a dog.