Steven Ricke talks about prevention of bacterial diseases in poultry

I'm a poultry grower in North Alabama we grow for 9 weeks. Most of the first 5 weeks go smoothly. Then i start having a very hard time try to keep the mortality down I try to find a product to lower the PH and keep it down to hopefully help with the dermatitis that seems to keep coming back every batch. Really cannot decide if dermatitis is the main issue or if something else is stressing the birds at that time but either way I think it would be best to have the litter at a lower PH Level to help keep the population of clostridium and other forms of bad bacteria that makes dermatitis more likely to get.
Any information or ideas would be appreciated
I products I have used
PLT and PWT at the first of the batch and has put some out with chickens in the houses it lowers the PH but quits working
Litter life
Iodine that u run in the water