Tomato Probs

[porshiepoo]

Does anyone have any idea what's ailing my Tomato seedlings?
Their growth is quite stunted - they're approx 6" and the underside of the leaves is tinged purple (it's not a mould though). The top of the leaves looks blotchy too but not with purple, it's like a yellowy browny spotty.
I don't think it's a Phosphorus deficiency - there's plenty of BF&B in the pots and the greenhouse doesn't get cold enough to create cold soil which would prevent the plants being able to take up the Phosphorus. Unless leaving the greenhouse open at night would make it too cold for them?
Could it be ventilation? The greenhouse has a door left open and 2 windows but the windows and door are all on the same end so the other end of the greenhouse can get a tad warm.
I'm really stumped and totally cheesed off, I never had any problem like this last year.

[Scunner]

Usually if the leaves have a bluish tinge, it is cold. I always try and keep their feet war until they are well established.

[porshiepoo]

Thanks for that Scunner. I guess it's still a little too cold to leave the door open at night and perhaps that's what the problem is.
The tinge actually comes from being unable to absorb the Phosphorus when the soil/plant is cold.
I just didn't think the greenhouse got that cold at night.
The growth is really stunted too, if they don't pick up soon I'll have to chuck em out and replace em.

Thanks anyway.

[Kevin Milkins]

I stand my pots on polystyrene and they seem to like that.

[Anji]

I set some of my plants on polystyrene over the winter in the potting shed, and was amazed at what actually survived the winter. One petunia is covered in flowers now, but in the past I've always thrown them out at the end of the year and bought new ones in the spring. Other 'annuals' survived as well.
I'll certainly be repeating the process at the end of this year.
Definitley worth trying with the tomatoes.