Here's a quick cheesemake guide for cheddar:
1) Culture milk at temp, should be around 88 degrees.
2) Wait for pH change of .1-.2. Rennet. Measure flocculation, use 3x multiplier.
3) Wait for total time until cut, check pH, should have another .1-.2 drop. If the drop is more, you have added too much culture and need to take drastic measures (more on that below).
4) Cut, check pH. If pH drop accelerating, proceed with the drastic measures.
5) Heal curd for 5-15 mins, then cook to 102 degrees over 30-45 mins until curd feels right.
6) Drain whey. pH should be around 6.0-6.2. If the pH is below 5.7, press with a light press so you can mill and salt quickly.
7) Mill and salt at 5.3-5.5 pH. Use the right salt amount. Final salt should be at least 1.5% of weight, and not more than 2.5%.
Press
Now for the drastic measures. If the pH drop is fast and accelerating, you are using way too much culture, or you are using a strain that acidifies too fast. Switch meso strains and/or use less culture. If you've already added the culture, you need to cook those curds down ASAP and press and salt. The way to do that is to cut them smaller than normal and cut them using a smaller multiplier. You will get a drier cheese, but the paste will still be OK. Use a 2x multipler, and/or cut to 1/4" or slightly bigger so the whey is expelled faster. Then, raise the temperature faster and to 103-104. That's the high end for meso, and they don't like the high temps, so acid production should decrease.
In this case, you already said what went wrong, you ripened for too long. I also think you're using a starter that acidifies too quickly or too much starter.
