Oh dear, that looks really bad. We can' t say what you are doing wrong unless we know what you are doing. I can only suggest it has been terribly overwatered or boiled somehow. Is it in a hot window? What is it planted in? Can you show the whole plant? Fuchsias need warmth but not high temps, light but not blazing sun moisture but not drowning.

No, it was indoors the whole time. And I certainly didn't over water it, I watered it once in a week and a half. I waited until the soil was dry. There are new leaves coming out of a bunch of points on the stems. Maybe it was damaged in the greenhouse but didn't start to show it until I got it home? Temperatures have been in the 60-70s and I had the plant in full shade. The greenhouse had it in full sun. I'll take pictures later

It needs to be outdoors. This isn't a houseplant.

I know, it was just too cold in my area to put it outside until a few days ago. We had a warm spell for about a week, then the temperatures dropped again

Can you put it out now? They are happy in 50s and will tick over lower.

Yes, I can put it out now. I took all the damaged leaves off and sprayed it with fungicide. I've been reading that botrytis loves fuschia plants. It does have some new leaves poking out where old leaves fell off. I'm posting some pictures now. These are under indoor light (it's night here right now) but it's going back out after I take these

Good grief that looks absolutely awful. The poor thing is terribly starved of light. When you say you had it in full shade was that indoors? That would be far too dark for it. And it doesn't need fungicide. There's no sign of botrytis. Get it outside in a sheltered dappled shade spot asap and leave it in peace for a while. And don't remove damaged leaves. Even those blotchy ones are still photosynthesising. Leave all the leaves on it until they drop of their own accord. If they're dead they will fall naturally.

FWIW, I've had 2 or 3 fuchsias that survived freezing temps for weeks when they were well under a porch roof. They were well inside the eve, about 4-5 feet inside, but they did it with no after affects seen.

I also overwinter Fuchsias at quite low temperatures, either in an unheated porch or up against the house walls, but the op was in zone 6, not California or the U.K. Their problem was lack of light, not low temps.