What do you fertilize it with?
More harm is done to plants by over fertilizing than by not fertilizing at all. But, it doesn't sound like an over fertilizing problem...but more of under watering. In the wind and hot sun, it probably needs to bew atered twice a day. The bigger a plant grows the more water it uses and the more you need to give it.
Inless you are using very very dilute stuff, lay off the fert and water more...or take it out of the hot windy place at mid day...but that's a pain!
Linda C

I fertilise with Miracle Grow every week and water once a day. Maybe I will water it more and see how it goes. Thanks for your help.

I have to wonder if it might be the opposite problem--overwatering. This can kill a plant very quickly, with symptoms very similar to underwatering. Calibrachoa does best in a well-drained soil and is moderately drought-tolerant; it's probably best to let the soil dry out slightly between waterings. Unless the pots are drying out every day (especially in zone 5, and this early in the season), there is no need to water that frequently.

How can I prune the Million Bells so they will get a fresh start as my beautiful basket now look so sparse and so many dry leaves..I did water and fertilize with Miracle Grow every two week...1 tblsp to 1 gallon of water. Plus did water daily...as the soil was dry.

Dry leaves mean the plant is burned.....either from not enough water or too much fertilizer.
Water more and cut out the fert for a month and then resume at about 1/4 strength.
Linda C

Another problem that can occur is too much success. That is, the plant outgrows the container it came in from the store and needs to be potted up a size (or two).

Mine are still going strong but are requiring religious watering by now, twice a day if it is over 90. I do fertilize every day, once a day, with 1/4 teaspoon Miracle Gro or other liquid fertilizer to a gallon of water. This has worked for me for many years for heavy and continuous flower production.

Thank you everyone for your suggestions I do deeply appreciate your advice but it looks like my plant is going from truly beautiful to truly ugly and I have tried it all..