Indoor bush tomato seedlings stalled

[BambooWhoosh]

Please could you give me some advice on my indoor tomato plants? The seeds are the 'house tomato' seeds on this page...
RealSeeds

I germinated them in the airing cupboard in the spring and then moved them to the windowsill. They produced lovely seedlings. That was well over a month ago. Some of them have got to about 18cm but have stalled.

I live in SE England and the weather has been a bit rubbish but they are on a south facing windowsill and the temp is about 18 deg there. I've watered them when they are dry (not too much!). There is no sign of mould (damping off?) but they are just not progressing.

I used this compost for planting Field23 as it seemed the most suitable at my local garden centre that was peat free. I thought it might be a bit 'solid' so I put a little extra grit in to aid drainage.

If the plants have run out of nutrients I could feed them but I thought I wasn't supposed to do that until the first flowers appeared?

I tried contacting RealSeeds but they say they are a small setup and can't respond to gardening queries. I don't think the seeds are defective as they germinated quickly.

Any advice very welcome!

Mine (not Real Seeds) have stalled as well. I think it's the lack of sunshine.

It's the cold, gloomy weather, everything is so behind this year.

Are they still in the same pots? How big are the pots?
Pot them up into much bigger pots with good quality compost. Feed regularly with a liquid fertilizer.
Put in a cane to tie them too.

They also need plenty of natural light, have you a conservatory or glass porch? That would do,

Where are they going to grow later?

• If in pots inside, I think they may struggle a bit - it's generally too dark inside for them to keep growing
• If in pots/grow bags in a greenhouse, I'd get them hardened off and into their final pots/bags and into the greenhouse
• If in the ground outside, I'd harden them off a bit and then plant them out as soon as possible

Are the current pots filled with roots?

• If so, it suggests they have outgrown them and need potting on

How long have they been in those pots?

• If about 6 weeks or so (it sounds like it could be) then I would start feeding them now if I wasn;t going to pot them on straight away

If the compost is a bit woody I've been told this can 'lock away' nitrogen (as the wood continues to rot) this will stall the seedlings. I don't think there's anything wrong with feeding them, some multipurpose compost come with those slow release fertiliser beads already in them. My tomato seedlings were also stalled (and yellowing a little), some Tomatorite has picked them right up.

@BlueChampagne @TonTonMacoute I thought as much 🙁

@averylongtimeago I potted them up from seed pots into 14cm pots a couple of weeks ago. They seemed to have a healthy root system but they were peaking through the drainage holes so I put them in larger pots. There are no roots visible now if I look under the new pots. Please could you tell me a good quality compost if you think the one I used may be lacking? They are on a south facing windowsill. Unfortunately I don't have a greenhouse or porch.

@AddersAtDawn It is a dwarf tomato plant bred for growing in pots on a windowsill. I've put a photo from the website below. I therefore did not want to harden them off. No roots showing. Only been in the new pots a couple of weeks.

@lcakethereforeIam I didn't notice that the compost was particularly woody. The Tomorite sounds promising.

The consensus seems to be that I should just feed them. The reason why I hadn't is that I thought I had read that you shouldn't feed before the flowers appear and as the compost said it had fertiliser in it I was ok but happy to learn. Also I should possibly replacing the existing compost with something else.

Thanks very much for the help.

I'd get another inch of compost on the top of those, and yes feed them because they will need it with the lack of sunshine and heat. Feed from the top and water from the bottom.

Thanks @AlisonDonut I'll get some more compost in the next day or two with the feed.