[Ma Lowe]

The bottom leaves of some of my tomatoes have mottled yellow and/or brown marks on them. They have been fed once weekly with comfrey tea so far and when I put them in the pots I put a mixture of compost, sand and BFB at the bottom.

Is this anything to worry about if so what can I do see photos below

[Springlands]

Are the rest of the leaves OK Ma Lowe. As tomato plants get older the bottom leaves tend to go a bit like your pics. I normally just gently remove them.

[Ma Lowe]

Yes the rest are a lovely green colour it's just the bottom ones. I am wondering it they are maybe a bit overcrowded as I have bush type tomatoes within about 15  plants I may have crammed too much in and ventilation may be a problem the greenhouse is a 10'x8' and only toms and cucs with peppers/chillies in there 

[Springlands]

The upper leaves do look healthy so it is probably just that the bottom leaves are getting older. You will need to be careful - as you say you do have lots of plants in quite a small space and it can cause problems if the air cannot circulate properly - there is nothing as bad as having fungal problems on your toms (unless it is blight).

[Ma Lowe]

I will put some of the bush ones out into the garden and just keep the ones I really like in the greenhouse. That way there will be more space 

[Springlands]

If you are going to move some of the plants outdoors you will need to acclimatise them for a few days. Toms do not like sudden changes in temps.

[Ma Lowe]

Yeah I know I will put them back in at night for a while.

[Headgardener22]

The lower tomato leaves on a normal healthy plant will die off, this is normal. I read somewhere that the reason they go yellow and mottled is that the plant is absorbing the nutrients from the leaves. Cut them off, it will help to improve the air circulation.