Hi Karen,
I do have alpine strawberrys in my garden in pots, i find giving them a light feed when mature allways helps keep the plants strong and producing good fruits, especially in the summer months when they are working hard to produce good growth and fruits. once every two weeks with tommerite.
Fresco i would imagine is larger in size, fruit and plant, there for it will have more of a need for water and feed.
Feeding can be very difficult to explain, i tend to reccomend halving the stated dose so everytime you water, the plants get a light feed, when they need it.
Check your baskets weight, if bone dry give 2/3 good watering to swell the compost when the compost is swollen i would then give a feed, otherwise the feed will be wasted.
If the basket is very wet then allow to dry out.
good luck, let me know how you get on
Mike Easom