For the past few years I've been working with the University of Florida's Horticulture Dept. helping them with their research projects where they use LEDs.
LEDs are all about thermal management. You have none.
Another issue you may have, that most LED designs do not have, is multiple colors at multiple adjustable currents. Using a different current for each channel is the biggest issue.
Five LEDs in a string is an odd number. You have to think about the power supply. What supply voltage will you use? You need at least 16V for these maybe 20V depending on the driver used.
More LEDs per sting running a a lower current are easier to thermally manage.
Unless you want to design your own driver you should consider using a Mean Well HLG-40H-54B and increase the number of LEDs to 16, or 21 for red. You will see that you will not get very much light from your board as is. The big problem being the lack of thermal management. The easiest way to remedy that is to use more LEDs driven with less current. You could use a HLG-40H-36B to drive 10 LEDs. I assume you need to adjust the output with some precision. The HLG type B gives you total control of the dimming with a resistor, potentiometer, PWM, or a DC voltage from 0-10V.
Another choice would be to use one power supply and a $3.50-$4.00 Mean Well LDD-350L or LDD-350LW for each string. These are 9-32V drivers which can power up to 10 LEDs. They do have a 56V LDD-HS series as well.
If quality of the dimming is an issue or you need more than 350mA (doubtful) the Infineon Technologies 1.5 Amp eval board EVALLED-ILD6150 is a very good driver at $17 each. The LDD modules do a very good job.
What ever you do, do NOT drive the strings in parallel without a balancing circuit (e.g. LM3466). Use one driver per string.
You could use a single power supply and a buck step down constant current regulator with a current adjustment (dimmer) to drive each string.
For the PCB. it is best to try and keep the tracks all on one side of the PCB minimizing the number of vias and gives you the option of MCPCBs. You could route the LED tracks along the sides of the board. Save the other side of the PCB for power, ground, and thermal management. Better yet do not put the daisy chain power tracks on the board.
I have a PCB I am currently working on that has 4 strings of 16 LEDs on a PCB that is 9mm wide. All LEDs tracks (15mil/.381mm) are on the bottom side. The footprint includes a via for anode and cathode. One footprint for each string. Footprints accommodate both Cree and OSRAM. The center pad is the thermal pad.
With four strings per strip I can mount two strips to a single heatsink and I can have up to 8 channels per strip. The heatsink double as the fixtures frame. If I need a lot of photons (e.g. cannabis) I can use copper water pipe as the heatsink and water cool them very inexpensively.
They can be routed on one side.
Use 2oz copper, it costs no more than 1 oz. unless you are going bare bones.
I used strips attached to a heatsink rather than a larger PCB. On a board like yours the inner LEDs are difficult to keep cool. And the spacing between the LEDs was wasted real estate. When I started with UF they had some larger boards (550mm x 100mm) with 6 channels of 3 LEDs with a separate driver for each channel.
This board could handle about 300mA with out the two fans running. At 300mA we could easily get 300 µmol/m²/s at a height of 400mm. This is a two sided FR4 where the bottom side is almost all copper used for free convection cooling. I think that is a lot of wasted real estate.
On my first LED strip I too put power tracks for daisy chaining. I do not do that any more. It's best left to wires to do that. Just wastes PCB real estate and the connectors got in the way. Never used them.
I used thermal vias on a FR4 rather than using a metal core PCB. I followed Cree and Lumiled's suggestions for PCB layout using copper to dissipate the heat without a heatsink. From the table of temperatures (below) you can see it did very little good.
For FR4 boards "everyone" recommends thermal vias with the heatsink mounted to the bottom side of the board. I found a different way. I mount the heatsink to the LED side of the PCB so there is solid copper from the thermal pad to the heatsink. I used the thermal vias to measure the thermal pad temperature.
The large pad is the thermal pad for the Rebel LEDs.
This is what 1 Amp with no thermal management looks like. I tried to skimp on the number of holes I had to drill in the heatsink. The board was not touching the heatsink under these two LEDs.
I extended the thermal pad to the edge of the board and added a screw hole for the heatsink to each pad. This way I could attach the heatsink to the same side of the board as the thermal pad and not have to deal with the thermal vias.
These cheap "Epistar" are usually not made by Epistar but other less reliable suppliers. The datasheets suck for these cheap Chinese LEDs. The datasheets I've seen specify a max temperature of 55°C where top tier LEDs are more like 150°C.
Below is a table of measured temperature and current for Lumiled Rebel ES LEDs. Without significant thermal management you may be able to run them with 200mA max before they over heat. See highlighted rows. The PPFD column is µmol/m²/s and this is for a strip of 16 Rebel White LEDs at a distance of 12-18 inches. The highest efficiency LEDs (e.g. Cree XP-G3 Royal Blue) have a max PFD of 2.77 µmol/s @ 350mA.
I do not know how many µmols you need, for tissues I assume no more than 150 µmol/m²/s. You might get that if the distance to this board was 50mm or so.
Do NOT use these cheap Chinese LEDs. They will be very problematic. You need uniformity and you will not get it from these LEDs.
If you are going to write a paper on your experiments it's possible no one will be able to validate your results becasue of the variance in the performance of these types of LEDs.
When evaluating LEDs thermal resistance of the package is very important.
The "Epiled" LEDs generate more watts of heat than light.
Improved efficacy equates to less heat.
If using blue red or other color LEDs, I would suggest using OSRAM Olson SSL 150 LEDs spaced about 20-25mm between LEDs. If white Cree XP-G3. These get up to 700mW of photons for each watt of electricity.