Thanks bamboo, did it from my phone, as you an see from 2nd photo I have been trimming of the yellow leaves.

Lots of plants in smallish pots - that's okay, but it means you need to water daily with at least a litre of water - if the pot's too dry, it will just spill out over the top, so you need to make sure it penetrates the potting compost thoroughly. Apply the water to the potting soil, and if the plants are not in hanging pots, make sure excess water is seeping out of the drainage holes at the bottom, and don't leave them sitting in water in any tray, empty that after 30 minutes. Water twice a day in this heat, morning and evening. Feed if you like, half strength tomato food in water once or twice a week max.

Continue to remove yellowed leaves - I'm seeing a few brown spots on those, so there may have been a fungal problem (not necessarily mildew) a time ago. If these are not trailing petunias, I'm afraid they will get quite tall and lanky and collapse in an ungainly manner over the edges of the pots - by the time they do that, its usually too late to cut them right back and let them grow again because after the longest day on the 21st, growth rates reduce compared to April and May.

The top parts of the petunias look quite healthy, leaves and flowers, so the problem was when they were smaller. Fuchsia looks entirely healthy, so you've obviously more or less got the watering right earlier on anyway. Not sure what that lighter coloured stuff is on top of the soil in the green pot though...tiny stones or granules of some sort?

Thank you, I used a mix of old and new compost when I potted them so maybe it was contaminated,( I have watered them everyday but not sure if it was enough) although I have 6 pots and some of them had fresh compost in, they are all the same, I am so disappointed as I have grown them over the last 5 years and if I remember had a similar problem last year only, but it was only in one pot and I did overcrowd it so thought that was the reason. Geraniums next year.

If you reused compost from the pot that had a problem last year, then yea, there might have been a pathogen in it. But I've had second thoughts about the feeding - don't use tomato food, you're better off using Miracle Gro General Purpose (square box blue powder inside) because there's more nitrogen in that, and that's better for leaves. Something to remember for next year perhaps. Works for geraniums too, and they're more drought tolerant.