AIBU to feel worn down by my parents' unhelpful visits?

[SarahAndQuack]

So, backstory: I have a nine-year old and 10-week-old baby; I'm a single mum. My parents are in their mid-70s. They have form for being pretty awful and I have been a broken record about not needing any help from them, while they've been on and on and on about wanting to come up, wanting to help, etc. I knew perfectly well that any such 'help' would actually cause enormously more fuss and bother than it would be worth, so I've just said repeatedly that it's not needed.

Last time my mum came up she was in such pain from having slept in a draft that she had to have wheat bags heated up through the day, had to have a great long whinge about the volunteering work she does, etc. etc., and had a long nap because she was so tired. That's fairly representative. They also do a good line in becoming furious if they feel they're insufficiently pandered to. I am very, very tired of it and there's a lot of history here, but it'd be a massive post if I went into it all. I'm just trying to explain that they're not loveable absent-minded 70-somethings who can be shrugged off with minor irritation and genial cries of 'oh, your dad, what is he like?!'

All this being so ... why on earth and I so bloody ground down by something relatively small?!

I was feeding the baby and my dad decided he'd like a cup of tea, so I asked my daughter to help him make one (ie., I asked her to help find the teabags and him to boil a kettle and so on). It took ages and I'm not even sure why, but, long story short, about 15 minutes later and after much back and forth about being unable to find things, he turned up with a cup of godawful lukewarm tea with a tiny amount of milk in. Obviously I just said thanks. After they'd gone I discovered they'd left their own tea cups in the living room (yes, I'd normally clear up after guests but they're my parents/I have a new baby), and my dad, for reasons best known to him, had take the teabags out of the cups and dumped them in the middle of the kitchen counter where they'd leaked tea all over bottles I'd just sterilised and left to dry on some kitchen roll.

My DD said she thinks he wasn't sure whether to put them in the bin or the compost bin, so he left them there. Not even on a plate (there is a little dish beside the kettle for teabags, FWIW).

It is such a tiny thing but it makes me want to cry. It seems like such a massive overreaction (I'm sure some of it is hormonal), but it just really hit me. AIBU to feel almost gaslit that the repeated desperate offers of help reliably end up with some kind of utter shit like this, where you feel as if you've stumbled into a parallel universe? Because, surely, no one in the right mind thinks 'ooh, I dumped used teabags on the clean counter; I've definitely been a net help here!' Do they?

I think the thing that still throws me is they would respond to this with anger or bemusement: either it'd be anger because they'd tried so hard to help and this was a tiny silly thing to mind about, or bemusement, because obviously anyone would struggle to find teabags, and how were they to know not to put them down on the counter. (And there would be much sharing of confused looks and a subtext of 'how weird that she thinks we would know not to do this thing').

This made me smile, my mother is just the same. I could write a book about it, but here's just one "for instance"
I'd make 3 cups of tea (one for her, one for DH and one for me). Now I drink mostly herbal infusions that don't take milk, so I'd put milk in 2 of the cups then put the bottle back in the fridge. She would (if I didn't keep a sharp eye out) wander into the kitchen, get the milk out of the fridge and put some in my herbal tea! WHY???
And if I remonstrated it would be all hurt looks and "I was only trying to help".

@SarahAndQuack there's no quick fix I'm afraid; in about 30 years you'll be able to laugh about it! I basically wouldn't have my mother in my home (I could cope with her behaviours a lot better in her home), so, as she got older, I dressed it up as "oh no you don't want to do all that travelling, we'll come to you".