New grow room -- pump/irrigation issues

Hi. Intermediate-level grower here, but brand new to indoors. I just built out a 7x7 shed into a grow room, you can see the full details here https://www.rollitup.org/t/build-journal-turning-a-7x7-shed-into-a-grow-room.922754/

TL;DR: I have a 3x3 tray in a tray stand over a 20-gal reservoir

Everything else in the room is working great, but I can't get enough pressure into my adjustable drippers from the pump. For the pump I have tried both the EcoPlus BDP585 bottom-draw and the Eco 633. Both exhibit the same problem.

The system goes:
Pump
1/2" fitting
13" of vertical poly 1/2" drip irrigation hose
1/2" elbow turning to horizontal
42" of horizontal 1/2" poly drip irrigation hose that is capped at the end
1/4" barb into the horizontal hose run
About 20" of 1/4" hose
Adjustable dripper

I originally had 8 drippers, but shut down 7 of them so I could locate the problem, still very anemic pressure.

However, when I uncap the end, there seem so be a pretty rapid flow. I'm starting to think that the problem is the 1/8" holes in the barb and the dripper. The barb is one of these:



And the drippers are these:



Any thoughts on this?