my Gardenia is growing fine - no flowers yet
I noticed the new born leafs looks funny
is this indicate over heat ? lack of vitamin or a need of water ?
It could be the things you mention, but if it were mine, I would suspect mites, which are very tiny, invisible to the naked eye, but suck the juices out of the leaves, distorting them. Mites do very well when it's hot and dry.
I had leaves like that on a jasmine this spring which I decided were mites. I would suggest cutting off the infected parts (your plant will branch below the cut), then spraying it with an insecticide, neem oil, or if you can't get either of those in SA, use a soapy solution to wash the plant thoroughly. You would want to repeat after three days or so, then repeat a third time to make sure you get every one. Soapy water will drown mites and other insects.
Regular misting with a hose might help raise the humidity around the plant and prevent a recurrence.
Your new leaves should come in clean and normal, signalling an end to the infestation. If not, you may want to repeat treatment.
i have been spraying my plant with insecticide freqeuntly since i have Lemon tree on board so they all share the bottle
my new theory is excessive water spray may dissolve the natural oil lead to this ?
Possibly. Excessive use of insecticide will also breed resistant strains.
It's also true that insecticides may not kill mites, as they aren't actually insects, but mites. Look up "spider mites" on the internet to read about them.