Sweet peppers - advice please

I don't feed then while they are small, there is enough feed in the compost for now.

How do you usually grow them on from now - it may give a clue as to why they don't do very well.

I grow mine in a cold greenhouse, sometimes in pots and sometimes planted in the border.
At this time of year they go out into the greenhouse during the day, for the light, and come indoors at night until it's reliably above 10C at night.
They are potted on each time the roots grow out of the bottom of the pots. I don't feed them til they start flowering.

I chuck mine out into a bed on the lotty, and let them get on with it. Most years it works great, apart from last year which was a disaster. 2014 got 17 KG from 20 plants, a little less the year before. I cant get to my plot every day, so a greenhouse or polytunnel would not work for me. Out of all the plants i grow, they are the ones that require the least attention!!

My method of growing sweet is the same as the normal/ hot & super hot chillies.
Mine are sown earlier as I have a grow tent and LED lighting system in place so they are flowering now as we speak although I nip the flowers off until they go in the final pot.

I start them off using the Jiffy pellet then when they go into the first pot just water for the first two weeks.

At this point I then start to feed, I swear by Maxicrop growth stimulant, seaweed based it really does produce a lot of root growth, I use 1.1ml to a litre and feed every two weeks until they go into the final pot which will contain perlite, once in the final pot I switch to the wilko fruit and veg feed which again has the seaweed with magnesium and feed weekly.
As regards the fnal pot, I use what is known as the Hercules pot, it is a type of air pruning root pot with the size at 12litre, compost is as mentioned mixed with perlite.

Thanks everyone, so basically I am on the right lines and will keep trying - it may also depend on geography to some extent too. Overwintering might be a plan, will try that!