Are they in containers or in the ground? Strawberries in containers are very prone to being killed by vine weevil grubs - they eat them off at the roots and the poor dead plant just lifts cleanly off the surface of the compost at teh end. Have a root about in the compost and look for little white c-shaped grubs with brown heads (or sometimes you find them when they've started growing their legs).

thanks very much, will do that first thing tomorrow, hoping i sort it as really looking forward to trying some!

sorry forgot the say in the message they are in containers