MYA QT Harsh smoke problem

[Kashmira]

Firstly, I have just started smoking and so my set up is really simple so it would be great if I don't get bashed up for the kind of hookah I am using. I own a Mya QT S class. I use it along with a big sized clay phunnel bowl by a company named Elzara since that was the only phunnel bowl I could find in India and a silicone hose. This was the first time I used natural coals and I used 3 of them judging the size of my bowl. However, I removed 1 coal once it began to get harsh but it didn't work. Water level was a tad bit more than half the base. Foil was a proper hookah foil which is thick enough. Holes were poked by a thumb pin. The first pull was okay but from the 4th and 5th pull the smoke becomes too overpowering on the throat. As if it is a lot of flavour blasting in my throat. Before this I have smoked on those cheap pumpkin ones with natural coals and it was pretty good. But everytime that I have smoked on a Mya, I somehow don't tend to enjoy the pull and find it extremely aggressive and it makes me cough a lot. 

According to me, I have shortlisted a few problems that might be the cause. 1. As I said I use pre cut foil it might not be big enough for the bowl to get a perfect seal, causing a leak. 2. The grommets that I used for the bigger bowl are cheap quality and are burning during the smoke session. 3. The foil is touching the tobacco causing it to burn. 4. There is a leak in the downstem since I might have not screwed it in tightly. 5. The coals might not have been completely lit or may have become old. 

It would be great if you guys could help me out  thanks