Okay, than it'll be easy to explain, I'm glad that you have so much motivation and passion for scanlating this manga, here is my suggestion to you, a simple trick that won't take more than a minute for each page, how your page from ch.28 looks like on release:
And here how it can look:
Cleaner image, with closer black colors. All you need to do in photoshop, is go to Image -> Correction -> Levels, or if you use short cuts it's a Ctrl+L
Adjusting levels is easy, here is what original scan level looked like:
And here is adjusted levels:
You use pretty good scans, that dont need alot of additional steps, and with this bare minimun quality of releases will get higher. Also another question, why is your scans in jiff format?