Two things. 90gr by weight is a heavy charge. Try around 100gr by volume. I'm not sure what weight that would be, because I just use a volume to measure the powder.

The second thing is T7 will leave a crud ring about where the bullet is loaded. The more powder you use the worse it gets. I'm not sure you're getting it all out with just a dry patch. Try licking a patch, and running that down first. Followed by a dry patch. If you don't want to lick a patch use Windex. No need to soak it. Just one spray will work.

If you decide to lick the patch. Make sure it's a clean patch.

What primers are you using?