If you have sticky leaves this means that your plants are infested with sap sucking insects, probably aphids, possibly scale insects. You will find them mostly on the undersides of the leaves. Treatment depends on what they are, though the systemic insecticide imidacloprid is effective on a range of sap suckers.

Agree with the above - unless the plants in your basket are petunias - these are naturally sticky as they grow. When you say well watered, if your basket is hanging in full sun, and is at least 12 inches in size, then it will need a litre of water in the early morning, and another litre in the evening every day while it is so hot. If the litre mostly runs out, that means the compost has got too dry and the water just runs off - to correct that, water, wait 15 mins, water again, wait another 15 mins, water and repeat as many times as necessary until the compost is sodden all the way through.