So I planted loads of different plants at Sanctuary and I had about 18 food. I did a couple of missions and added a supply link to another settlement. Later I check the food again and it's only at 6, I plant more plants and it's still at 6 and the settlement isn't growing.

The only thing I can think of is I'm playing on Survival difficulty and sometimes the rain is radioactive, is it killing my plants or something? In that case, do I have to build shelter for the plants?

Any idea what I'm doing wrong or is this a bug? Appreciate any help, thanks!

Ok so I went back to an old load and basically as soon as I assigned a person to a supply line with a new outpost, my food went down to 6 and wouldn't go back up. Any idea why this is happening and how I can fix?

Guessing you assigned the dude that was tending your food to be your supply line. You have to assign settlers to food for it to count.

well I couldn't assign the original 5 settlers to the supply line, so I picked the new one that arrived. As soon as I picked that person the food count went down. I go back and load an old game and if I don't send that settler to the supply line I have a food limit of 12 but no new people come even though I have enough beds and water. So how do I fix this problem?

Take some of the original settlers who cant be assigned to supply lines and send them to work the crops?

How do I do that? When I am in workshop mode and want to issue a command to them my only option is to ask them to go somewhere. I'm playing on PC btw.

you tell them to go there by selecting them select assign then go to the food point at it and tell them to go there as it is highlighted. each farmer can only produce 6 units of food so just assign prestons people to farm

Cool, finally sorted the problem out. Thanks very much for the help!

Did you recently get any fat settlers? Sometimes they eat a lot more.......hence why they are fat.