Planted mix of ericaceous and non ericaceous plants - help? New build!

[justawoman76]

Last year we moved into a new build property.
The garden was a blank slate so I had large raised beds built. They just filled the beds with the 'soil' they excavated from the rest of the garden.
To be honest, I didn't know anything about plants, I just bought what I thought looked nice and was big so that it filled the space quickly.
I planted lots of cordylines, fatsia, lavendar, a magnolia, ivy, holly, heucheras, hebes, phorniums, cotoneaters, skimmias, rhododenrons, laurel, photinia red robins, aucuba japonicas, heathers, and lots more.
I am happy with the way it looks this summer but upon doing more research I seem to have planted a mix of both acid loving and acid hating plants. I'm noticing a few yellowing leaves on some of the plants (mostly the holly) and have done a bit of reading it seems it could be that I need to supplement the acid loving plants with iron or ericaceous feed.
How will this play out given that I have a mixture of plants? Have I doomed myself to never having a plant that is truly going to flourish? Can you 'spot feed' certain acid loving plants or will it leach into the soil?
This year I have dealt with some kind of fungus on my photinia which I seem to have treated (new leaves coming through without black spots) and on my magnolia.
I am learning more every day.
I will attach some pictures of the garden so far.
For reference, the soil is very clay based and crap, typical new build rubbish. STILL finding bricks and all sorts even though I dug it out for days and added in bark mulch before I planted anything. Should have added better soil at the beginning but I was very ignorant and just wanted quick results.
Lost a few plants over the winter due to ignorance and not protecting with fleece etc when I should have.
Surprised how much I am enjoying the garden, last house we basically had only a lawn and some pots! I've probably planted some stuff far too close together in my haste to make it look established, so may have to move some things around in a year or two?
Thanks for any advice.

pics

more

last one.
Couldn't figure how to get all pics in one post, sorry.

Ivy is looking a bit brown too, not sure if under or over watering?

Missed these ones. One of these is the non flourishing ivy. It is sending out shoots and trying to climb the fence so I have hope for it, there's just quite a few leaves looking almost rusty in colour and crispy at the edges.

Can you get a clue from what is thriving locally?
Eg we live in an are with a lot of trees ; so woodland really with no chalk in the soil. Acid loving plants eg rhododendrons are very happy but many other plants are too . Most of the things in your garden are reasonably happy here. I haven't had much luck with lavender which I blame on drainage conditions rather than the soil and it is always the case that you will lose some plants . If something isn't thriving it might be happier elsewhere.

Can you 'spot feed' certain acid loving plants or will it leach into the soil?

We seem to manage it with some of ours eg rhododendrons- I think it may help that they're in a heavy clay border, I don't think that leaches away anywhere near as fast as a free draining soil would.

You can get soil testing kits from the garden centre, but sometimes you can get away with a mix. But it might also be the heavy clay that is preventing some plants from getting their roots established. When I moved house, I lost a lot of plants because I didn't take drainage, light levels, etc into account. But some when I dug them out, hadn't grown any roots at all, they were still in the shape of the pot I'd bought them in. I think because we are also on clay, and I didn't give them a big enough planting hole (or backfill with compost always, if I was in a hurry). For your acid lovers, it won't hurt to try an ericaceous feed, and maybe mulch them with ericaceous compost. Your other plans should be fine.

I think everything there is looking fine. The holly is just showing the lighter coloured new growth.