Pyracantha leaves suddenly falling

Hi

I'm new to the art of bonsai, so I'm unsure if I need to worry about my Firethorn or not?

I went away for 3 weeks and had a friend look after my two bonsai (Firethorn and Snowrose) and they were doing well until just less than a week ago when my firethorn started losing it's leaves, I'm trying to figure out if its purely because my friend over watered it or left it outside for a bit too long ( it's winter here, so he kept in inside during the evening and moved it outside during the day) or something that will be sorted on its own now that I'm looking after them again.

I do know it has gotten more sun these past 3 weeks than when it usually does, and the climates have changed because I took them home when it's quite a few degrees colder.

My Snowrose is doing brilliantly, so I know my friend hasn't been negligent.

I've gone back to where I stay at uni so the bonsai will be receiving their usual watering, sunlight and temperature, I'm not sure if I should wait it out or if I need to take action some way or another?

The leaves seem to have discoloured half way down the leaf to a pale green and then a line of brown and after that the leaf looks normal, and my tree was swarmed with leaves and now has very few. I did pull off quite a few unhealthy leaves (and so did my friend while I was away) but I've left some because I'm scared i take off too many leaves and make the situation worse in any way.

Please help? Do I need to do something or shall I wait it out for a short while?

Will post pictures

Plants do not like being moved around a lot. Certainly not inside/outside swapping on a daily basis. Choose one, and keep it there.

I would never bring a firethorn inside. Not sure what winter you are getting, but it woun't be worse than what we get here.
That being said. If you get cold weather (sub-zero temps) you will need to make sure the plant gets used to the temps before exposing it to it. A normal temperature cycle, staying outside from late summer is required. So do not put outside unless you do not get frost.

Is the house heated?
When did you wire it?

What kind of winter temperatures are you getting where you are TLianeBorner? It would be helpful to know daytime and night-time levels.

Yes I know they don't really like being transferred inside and outside the whole time so that's why I thought it might not be a big issue, and it was just that that made the tree lose its leaves because it was very disturbed or something.

At home where my friend looked after it during the day the temps are around 16-21C degrees and in the evenings we get close to 0C, we do get frost at home though so that's why my friend brought it inside, and our houses aren't heated but it was slightly warmer, around 9C.

Here at university where I've brought my Bonsai back to the day time temps are around 3C degrees warmer.

The tree was wired in April and I'm going to take it off soon in August/Sept when Spring comes along because I'd like to change the shape a little.

I bought the tree in around March from a Bonsai nursery.

TLianeBorner wrote:The tree was wired in April and I'm going to take it off soon in August/Sept when Spring comes along because I'd like to change the shape a little.

dont go by the calendar when it comes to wire removal...

when it starts to bite into the wood it is a little, but not too, late to get the wire off...
best to get it off at the first signs of biting in.

TLianeBorner wrote:during the day the temps are around 16-21C degrees

HAH!! You've just described my summer temperatures. LOL

I can't speak for your part of the world but those winter temperatures winter are far higher than the ones I experience here, and my pyracantha are quite happy outdoors. I think the constant moving in and outdoors may be the problem.