Hi, I have the new kerrii that is developing these brownish patches, and I have already treated it with a fungal gun yesterday and this morning It's seem to be spreading... do I need to cut the leaf off? The underside is normal, just the top has these patches and only on this leaf. It was in a prop box with high humidity as I was trying to develop more roots, with no air flow..( sorry I'm new at this) and so I think it developed this fungal. Is there anything I can do more to it?? Also it's starting to grow nice roots and new leaves are coming so so far it's still happy? Please help as I don't want this to spread...

Thank you for attaching photos of the fungicide as that's a new one on me.

The product you used is a systemic - that means it will take a few days to work its way into the plant tissue before having any affect on whatever you sprayed. I don't know that you had a fungus because I wouldn't expect it to show up on leaf tops instead of bottoms and because there's no sign of it now. It could be the plant is suffering a little edema from the high humidity and constant moisture in your propagator. Or that's an old leaf and it was time for it to go.

Either way, Yate's Rose Gun is for roses. It could be it was a little too strong for the Hoya and the leaf is suffering some chemical burn, especially as only the leaf top is affected and it happened overnight.

I wouldn't cut off the leaf.

For a beginner, you are doing a good job.

Thank you daisyl for your reply. I used this rose gun because it was recommended and the shop said Hoya is classified as an ornamental ( we don't hv much other option in New Zealand) I also applied some cinnamon on it today just in case. Day three and under side still no sign of black spots so hope it is not fungal. does fungus always shown on the leaf both side? Would you think it's sun burn instead? But I have only just given a little direct morning and late afternoon sun, other times it's only indirect sunlight. I'm so confused...

That's not sunburn. Sunburn would cause white patches.

My best advice for you is to stop treating invisible ailments or you will kill the leaf.

Thank you Daisyl, I've already washed off all cinnamon off this morning and the the patches doesn't seem to hv spread further, underside still patch free so hope it's ok. I'll keep an eye out for it and repeat the spray if it's spreading again.

Can I also ask another question? I have another kerrii which I own for about 2 months. The first week I watered it it caused a lot of edema. The seller told me to hold off watering for a week after it is bone dry, which I did. I watered it 2 weeks later, it was dry after one week (summer over here in Nz) and the edema was less after watering. And the previous edema marks has faded.
I watered it again after 2 weeks and this time the edema appears again even after 1.5 weeks the marks is still showing more and more. I'm confused as to what I should really be doing and how exactly do I reduce overwatering. I've attached the before and after photo.
Any advise would be so appreciated.

If your soil is taking that long to dry, its the wrong soil. Hoyas are epiphytic so require a potting medium that gets thoroughly wet than dries quickly. What is your Hoya planted in?

It's in orchid bark, cactus soil and perlite in equal part I think. Shall I change to a more bark ratio?