You could be over feeding as this causes the plants to produce lots of leaves and not much fruit.

This year I have grown veg in pots and some in the borders. The tomatoes in pots had lots of foliage and I have had to thin them well back to allow the fruits to ripen.

These were fed with Tom feed and don't have as much fruit as the ones in the borders who have their roots in soil that has had lots of manure and soot put into it over the years.

Also the ones in pots struggled with dry conditions and then lots of rain.

It was the same with the peas and my peppers failed altogether.

You don't say where you planted your other veg, if outside was the soil well prepared the year before? Or did you lose them to the slugs or viruses?

Earlier in the year I put my broad beans in pots outside and lost them to frost, as the flowers didn't set.

Most vegetables do not need to be grown in a greenhouse but outside and, preferably, in the soil. Feeding does not help if you have poor soil you need to work good organic matter into it - your father had the right idea using muck! Personally I've never had any success growing potatoes in any sort of container but they do fine in the ground. Remember to well compost the trenches and to keep ridging them up. I wonder if you could add a photo or two of your non-productive veg. to your question - it might make it easier to see what is going wrong.

Remember to give them enough space and enough sunlight to get produce. If you are growing a dozen or so plants in a trug, that would probably be too many for the amount of soil you can cram in there, unless it is something small, like radishes. Fruit bearing veggies, such as tomatoes, peppers, and peas, also need pollination to produce edibles.