I am not sure if you planted a variety of radicchio that stays in a leafy form or if the warm weather is causing the plants to form lose leaves rather than a head of foliage. Either way try to keep the plants cool and well watered and harvest the outer leaves often to keep the new young foliage coming. This is a green that is best planted early in the spring when the soil is cool. Many leafy crops suffer and bolt or go to seed once the weather warms in the summer. Keep growing, Marianne Binetti