It should have you concerned. I have 2x3000lph central heating pumps feeding about half the number of plants you have there. I find that even then I have issues with insufficient flow. One issue is that the valves that feed each tray in my system get clogged with little bits of crap (broken off parts of root, algae, precipitates) and there is not enough back pressure to clear it so that outlet stops flowing.
I would start by figuring how much flow per plant I want. Get one of your buckets and set the flow to it to be the rate you want. Now measure how much volume that is in 1 minute.
For example, if you fill a 2 litre jug in 1 minutes that is a flow of 120 litres per hour (2x60).
Once you know your flow per plant per hour, multiply that by 30 (you have 30 plants as far as I can see) then add 25% extra for losses (this is a guess, if anyone can give more a firm answer here please do), both from the length of tubing and to allow for some spare for when the pump gets old and tired.
So, using the example above again, at 60 litres per hour for 30 plants you would need 1800lph and 25% on top would be 2250lph.
I just tested my flow rate and it fills a 500ml glass in about 14 seconds. When I look at the flow it is not much more than a trickle from a 15mm (1/2") outlet. This is 28 seconds per litre so (60/28)=2.1428 litres per minute. 2.1428*60=128.5lph
I find this gives a good flow to allow plants to grow vigorously. I would like more. Specifically more pressure to clear blockages but that is not relevent to your issue.
128lph*30 plants would be 3840lph, and with the extra for losses 4800lph.
I suspect your 1500lph pump will not let your system provide the benefits it is capable of and you would get a better result with a larger pump (or two).
One thing to be very aware of is the head on your pump. If your pump has to make your solution rise from the floor to your tank, that height is called the 'head' and it is normally measured in metres.
Most pumps at a 1-2m head are pumping half the flow they do at a head of 0.
The max head on an ecoplus 396 is 1.95M. That is the height you could hold a hose and no water would come out of the end. There would be no flow at all.
Here is the chart showing flow at various heads. Your storage tank inlet looks to be about 4ft (1.25m) high. At that height, your pump will only supply 600lph. With losses from the length of tubing, you are looking at much less than that.
That is about 20lph per plant, around 20% of what I would consider to be decent flow.
Always look at the head chart on a pump, it is the only way to know what flow YOU will get in your system.
Here is the head chart for my pumps. Ignore the other lines, they are different settings. The one to look at is the solid black line which is the highest.
As you can see, they have a good head (4m) and will still provide 50% flow (1200lph) at over a 2m head. I placed a second pump at 1m to keep flow up at the 2m height I need for my particular system. As each pump only has a head of 1m this means I get roughly 2300lph at a head of 2m (1m3=1000lph). Dividing that by the 18 plants in the system gives (2300/18=)127.777lph, very close to the direct measurement I just took. The extra from the real world measurement is probably due to some outlets being lower than 2m, which would reduce the head as far as the pump sees it.
For your system, with 30 plants, I would say you need a net flow of 3000lph after losses, with the 25% spare that is close to 4000lph. This would get your system into the flow rate ballpark to allow your system to function as well as it should.
Hopefully, this information will stop you getting another pump which will also not be enough and to start looking at pumps capable of what you need them to do. You have a serious system, you need a serious pump. Not aquarium toys...
Please don't take this as criticism, you have done really well if this is your first watering system, just some timely advice.