This is likely the issue. How are your panels connected? All in series or ?.
Any shading on a series string, even a single panel can drag down the entire string.
The shadows are pretty long in your photo so you will not reach panel spec watts without sun high overhead.
I probably should have been more clear, (or less shadowed, haha ummm...)
Anyway, when I said shadows, I didn't mean the panels were in shadow, I meant there were moderate shadows - meaning there was discernible sunlight.
I have six panels, three connect in series and those two sets of three, connected in parallel.
You were right about the long shadows, as the day has progressed, the panel output did increased.
I think I might be overthinking things - my batteries are at full capacity now. More over - where before, the low voltage alarm had been going off in the evening on dull days - I've since added a third battery, and that's not happened since. (I also unplugged my fridge from the solar supply - that's back on mains now.)
My plan is, to increase the panels and increase the battery capacity so I can get more of the house off-grid.
I'd also like to explore the solar dump (hot water idea). I have more panels coming, so I can use those specifically for the purpose of heating water - if I can figure out how best to do it.
The plan is to go fully off-grid - so when my energy supplier threatens to cut me off, I can tell them to go ahead.