What kind of Lonicera are you growing?
Most plants become more susceptible to problems like Mildew and leaf spots if they are hungry. Try feeding the plants or repotting in fresh compost.
Not sure about cider vinegar, not something I have ever used. Might be better to try Rose Clear perhaps.
Also check for aphids, they can be the source of sooty mould which would do the plants no good.

OB is dead right. Most Lonicerias are susceptible to mildew. If you already have Rose Clear then give it dose of that. If you need to buy then Fungus Fighter will do the job. But just like mildew or blackspot on roses, you would do better by spraying as a matter of course before it becomes infected.

Thank you both.

So it doesn't seem it might be my fault by under or over watering?

Sorry, I have no idea which kind of Loniceras but they are different from each other. They are well established in big containers, so would be difficult for me to re-pot, but I will dress the top soil with some fresh compost, and feed it. I will also buy the Fungus Fighter and hope that it works.

Actually, I have had nothing but problems with these shrubs. When I planted the first one around 20 years ago buds would form and then mysteriously disappear. Simply plucked out of their sockets, not by birds or mice. After much research, I was told it was a nocturnal moth which visited in the night??? Longing to experience their beautiful fragrance, but wondering if I ever will.:-(

Is this the lonicera shrub - or the flowering lonicera ?
I'm guessing the latter because of all the shrubs i've grown of it don't get that on the foliage, infact they're as tough as old boots.
If the flowering version i would say too dry at the roots, and as they're contained i'd say even more likely.
Pot sizes should be at least 30cm top diameter and 60+ height.
Anything less just isn't conducive to anything other than annuals.

Infact, as they've been potted for many years i total repot would be in order now.

By the way, squirrels love pots, they'll ferret around in them turfing out all and sundry !

Thank you, they are both flowering, and each one lives in half barrel. One was planted last summer but the other is old. Foliage is good from early in the year, but then the mildew starts and all the leaves eventually drop. I have now bought the Fungus Fighter and hope this will save the climbers. So although I feel I have been fairly diligent about this, it seems I might be under watering, as opposed to over watering, it isn't so easy to gauge the correct amount.

I live right in the middle of a stone built village in the Yorkshire Dales, so sadly I don't see squirrels on the roof patio, which is all I have:-)