Greetings Fijiball,
The pH doesn't really affect yeasts and ACC are an indicator of general hygiene. For the easy one, which is ACC, you should look into better and more thorough cleaning practices, especially in hard-to-get places, personnel hygiene (hand washing, working uniforms etc). Also, you will need to check the responsibles for performing the cleaning, maybe it is lacking or not properly applied or wrong use of cleaning/ disinfection agents.
For the difficult part -yeasts- you must identify the source. One possibility is that the sesame comes in already compromised and making a dressing out of it, just makes it easier for the yeasts to grow. Another possibility is that somehow somewhere in your production line you have yeasts, maybe from residues that are stuck somewhere in the line. A third possibility, but a bit less likely if it is only yeasts, is you could have someplace in the production that is infected and you get spores in the product.
The blown bottle is due to the gasses produced from the metabolic activity of the microorganisms.
The first solution for all this is an inside-out detailed cleaning and disinfection of literally everything, so you can at least start aknew. The rest are applied as appropriate for maintaining the risk free production environment.
Regards!