Missing tits ?

Been at my new house 21 months now, and through all those months, up to the 2021 birdwatch, have had plenty of great tits and blue tits, and even an occasional band of longtails.  But since this year's birdwatch, when there were loads of sightings in my garden, there have been none.  I'm next to woodland, with an adjoining and flourishing hedge of holly, bramble and hawthorne, and I have had several feeders out all this time with my usual peanut contents.  What's gone wrong this year ?  

I'm not aware of any changes to the environmental conditions, and I don't see any starlings or woodpeckers (reported to be predators of greats/blues).  The garden is fully fenced and there are very few agile cats in the neighbourhood.  We have no more pigeons, robins, crows and magpies than in prior years, and no more grey squirrels seen in the garden.  I'm a keen walker through the nearby woodland too, and I've seen no raptors around this woodland.  The neighbouring bushes would normally see tits and sparrows flitting from branch to branch, but there's nothing.

My elevation is about 150 meters, and I'm on the edge of a new housing estate, in rural Leicestershire.

Any thoughts ?  What am I missing ?  Or has there been an excess of predation ?  The only off-the-wall item is that one of my neighbours has put some sort of preservative on their side of the fence, a fence on which the tits would sometimes perch. Might there be an issue of poisons ?  

Thanks for any help.