In most cases people use neem to fight insects there is a reason why there are dosages on labels.
I suggest f0llow them and for good reason like the product says
Neem oil by applying strong doses you can be blocking the stomata possibly impeding respiration.
And being said oil you have to make sure your plant has cooled down after intense 12 - 18 hrs of light
And when applying you need ample time for plant to dry up
Think of it like putting baby oil on your self then going outside and sun tanning :)
Same thing applies with plants .
I purchased neem once and used it for like 2 years just to get rid of the bottle it sure puts a nice shine on your plants
it surely does not make it grow better just looks prettier.
So just remember if your using it which in most cases are for mites then follow instructions make sure you allow plant to cool down and allow enough time before lights on for plants to dry up
And most importantly repeat 4 days later
and it might be good practice to raise your lights after the dose