it needs a good general feed. add a few slow release fertilizer granules now and then a few more in the spring. if you haven't any plant food then some Epsom salts 1 teaspoon in half a gallon of water] watered in will help too.

when did you last repot it? Perhaps it is ready to be moved into a bigger pot in fresh compost.

It looks mostly like nitrogen deficiency, which Epsom salts won't supply (sorry, Sbg). I would use a teaspoon or two of unflavored gelatin, instead, lacking a general feed for container plants.

I don't know what conditions this plant is growing under, but it's not thriving and may be beyond help. Read this article on how to care for holly bushes and the problem will become evident. I wouldn't venture a guess.

https://www.gardeningknowhow.com/ornamental/shrubs/holly/growing-holly-bushes.htm

yep could indeed be nitrogen but often as you will know Tug lack of magnesium prevents the formation of chlorophyll. and there is no need to be sorry or apologise to me.

either way it needs a good feed.

Hi Seaburngirl, I repotted it beginning of the year. I’m thinking that I may of fed it the wrong feed!! I used a feed for acid loving plants. Perhaps that’s where I’ve gone wrong. I have some all purpose so I’ll see how it gets on with that.

Something similar happened to my potted bay tree. A general feed greened it up very quickly and left me with a guilty conscience...

Pope_dot, I think that Seaburngirl sees better than I do! :)
I expanded the picture and took off my glasses (I'm nearsighted) to peer at it from a foot away, and the pattern of yellowing is consistent with both magnesium and nitrogen deficiency. If your all purpose has magnesium listed in the guaranteed analysis, it alone should do the job. If not, I would add Epsom salts to the all purpose as Sbg recommends.

Holly bushes are acid loving plants and require a soil ph between 5 and 7. The soil ph must be in this range for the bush to take up any nutrients at all. Perhaps alas that is the problem. Magnesium deficiency? Nitrogen deficiency? Rarely ever is the soil lacking in these nutrients. Even Death Valley is fertile enough to grow spring flowers. I'm thinking it's the ph. Try repotting your holly bush in a potting mix for acid loving plants - use something like Hollytone by Espoma. When the ph is corrected, then the holly bush can use all those other nutrients. The ph must be constantly monitored in a potted plant because it only has that limited amount. Fertilizer is also essential, but only during active growth. Don't give it fertilizer now. It's pointless anyway until you fix the ph. Too much will only burn the roots. I don't have high hopes for this bush but the garden centers will be restocking in a few months.