Greenhouse strawberries dying

Hi, I'm new to the forum, so I hope this is the right place to post.
I grew strawberries on the allotment last year - healthy plants which unfortunately never ripened as the local rodent population took all the fruit.
This year, I brought 18 of the healthiest plants home to plant in the greenhouse, hoping they would thrive in the warmth and away from furry nibblers.
I planted them out in growbags. One by one they have died, so that only 5 are left alive. I don't believe they have been over/under watered, and I have been feeding them gently. Any ideas why?

There are small draining holes in the bag, but maybe not enough. However, the soil had dried between waterings (but maybe only near the top). The bags are from LIDL and I wondered about the quality of the compost - it was very compacted and wet when I planted.