You’ve chosen some really great cheeses, John.
I can’t help you with Havarti. I’ve made a couple of them and just used the times listed on New England Cheese’s recipe. It’s a terrific cheese!
For Colby the last marks I used were: 6.6 at the start of the cook, 6.2 after cook.
For Gouda, ripen cut curd to 6.6, 6.4 after water exchange. At this point I press under whey 15 lbs for 15 mins.
If you do a Cheddar, it should be 5.95 at the end of the cook stage.
We’ve had some discussion of this on the forum not too long ago. A major factor in determining your pH marks is the pH of the milk you use. I don’t use commercial milk, and it may be more consistent; but with raw milk fresh from the cow there is a lot of variation based on the cow’s diet and the time of year. We’ve kind of decided that the important thing here is not the actual pH mark, but the amount of change in pH during the process.
Generally speaking, the lower the pH the more acid development, and thus the sharper the cheese. Also, more acid development results in a drier cheese. Play with it and find what you like best and then go with that. It’s not a question of what is “right,” but what you like best.
Hope this helps.