This is my 1st year having an allotment. It already had a sad tired looking strawberry bed in it and I took off some of the runners from the existing plants and bought a few more plants (marshmello). Didn't look at all well so I moved the bed added a few more plants (Judibell) still look like they are clinging on to life by the skin of their teeth. What have I done wrong? About 6 strawberries from 30 plants.
Regarding the new ones! did you give them a good soaking prior to planting them?
They may have been out of the soil for some time by the time you get them and quite often the moisture in the soil you planted them in is not enough to get them going.
The ones from runners sounds like they came from poorly stock as you mentioned; It already had a sad tired looking strawberry bed so it is not surprising the runners are the same!
They may be old plants which have viruses. In which case, compost them and get new. Strawberries are extremely tough, and I've revived completely dried out plants before now, by soaking them in a bucket of water overnight.