There are several posts ongoing from old crop to new crop when it comes to making fresh-cut fries. As you mentioned, the old potatoes turn out beautifully and the new crop is always a struggle. Briefly, old crop from Idaho is the Russet Burbank variety, and since it has been in storage all season the potatoes have lost a lot of moisture. If stored properly, they didn’t accumulate excess sugars, so they fry up perfectly. Russet Burbanks are a later harvest variety, where the new crop is the Russet Norkotah. These may have excess starch and sugars when coming out of the ground, being sorted and shipped out. The best way to offset them turning out limp and dark is to:

1. Rinse in water until it runs clear, to help remove the excess sugars.
2. Blanch the potatoes first (I bring this up because it is very hard to get a consistent fry without blanching).
3. Blanch at a lower temperature than you normally use. For example, if blanching at 325°F, try dropping the temperature 15 - 25 degrees and blanch longer at the lower temp.

Here are a couple of more detailed posts at this link:

https://idahopotato.com/dr-potato/why-are-my-fresh-cut-fries-turning-dark-so-quickly