[cc]

In green house. 3 raised beds. In 2 beds the sweet peppers are just not growing. (No sweet pepper in third bed). In one bed the sweet pepper is clearly on its way out now (see pictures) the tomato plant is also not growing in that bed. 2nd bed tomato doing great but sweet pepper doing nothing. Third bed has just one tomato doing okay.

[mumofstig]

They look as if the could do with a good feed, I'd use a feed with seaweed in it if they were mine....
I use Doff Tomato Feed Fertiliser High Potash with Seaweed and Magnesium for anything like that 

[Subversive_plot]

I think MoS nailed it.
The yellow especially along the veins are a magnesium deficiency indicator. Yellow can also indicate low potassium. The recommended fertilizer sounds like a good solution!

[cc]

Thanks ordered. Via ebay hopefully it will be here before they die. Twice the price of buying from wilkos but I am not in town before Saturday.  As an aside I have been using comfrey tea, no magnesium??

[cc]

What do you think to this product.
https://www.lovethegarden.com/uk-en/product/levington-epsom-salts-15kg
Added to comfrey feed?

Also in the same beds cucumber are looking particularly healthy?

[cc]

Am I getting this right: adding Epson salts to the ground increases magnesium?
I have added some to comfrey but only done one maybe to feeds upto now with it.

[hasbeans]

Am I getting this right: adding Epson salts to the ground increases magnesium?
I have added some to comfrey but only done one maybe to feeds upto now with it.

Worth a look: https://s3.wp.wsu.edu/uploads/sites/403/2015/03/epsom-salts.pdf

[Subversive_plot]

Am I getting this right: adding Epson salts to the ground increases magnesium?
I have added some to comfrey but only done one maybe to feeds upto now with it.

Yes.
Epsom salts are magnesium sulfate.