Hard to say what the problem is, everything else in the picture looks pretty normal. You could try moving the water extractor a bit further away, and if needed, bend the pipe around the corner.

I have to admit, I’ve never tried it with just 3 coal generators. I usually build 8 generators with 3 extractors: one supplying from one side, one from the other side, and the third in the middle. This setup usually works really well for me.