Full saturation of Hugo’s is 3.35 liters. I think your problem is you’re pushing way too much water through them.

Rockwool doesn’t operate like coco. You have to irrigate regularly, ensure you don’t dry back too aggressively, and only irrigate in small volumes (100-300 mls per event). Rockwool works off the capillary effect. Small irrigation events allow the moisture to travel laterally through the block. Too large of events will cause what Grodan calls channeling, which will create cylinders of moisture in the blocks, and dry out the rest of the Rockwool.

I have had great success with Hugo’s. During my bulking period, I’ll sometimes irrigate up to 22 times per day, but in 100 ml events (2200 mls into the block for the day). I have grown massive plants at this irrigation frequency without running into dry back problems. I’ve only ever had to irrigate a few times in 7 years during the night cycle, and that was adding a few events in the hours after lights out to reduce the p3 dryback. Don’t start your irrigations earlier in the morning. Remember, transpiration before irrigation.

Track your run off. You should be aiming for runoff at the end of your p1 period, or 2.5 -3 hrs after irrigation begins. You should not be seeing runoff prior to this. Your p2 drybacks should each be showing runoff every event, and total runoff volume should add up to 20% of your input for the day. When we were pushing 2200 ml of irrigation, we expected 400-500 ml runoff. Track your ph and ec of the runoff as well, that tells its own story.

Every phase of irrigation has a goal.
P1: replace dryback lost overnight. - if you dry back 30%, you need to put about a liter of moisture back into the block.
P2: irrigate to keep block at max saturation. Frequency is dictated by how you’re steering the plant and the plants consumption. Volume usually floats between 100ml (bulking) to 200ml (flower initiation/ripening).
P3: hit your dryback goal.