You can use a second psu if your first one is out of connectors...or near its limit on total power...but you need to follow a few basic rules for dual psu.... (atx psus...likewhat you are using now)

You can use a 2pin y cable that will start both psus at same time.  like this...  https://www.amazon.com/Qaoquda-Power-Supply-Adapter-Motherboard/dp/B078W4H16S/ref=sr_1_1?dchild=1&keywords=dual+psu+y+cable&qid=1610902119&sr=8-1

You must connect all mobo connections to one psu... (cpu / molex )

Each gpu & riser must be from the same psu.  Never gpu from psu 1 and riser its on connected to psu 2....that is a nono.

Thats pretty much it.

You can also do it with your psu (again only it hooked to motherboard)
Then power gpus/riser combos until the psu1 is full.  Again never combine psus to a gpu/riser combo.

Then for second psu you can use something like a server psu with a break out board....

https://www.amazon.com/579229-001-Platinum-Supply-Certified-Refurbished/dp/B07HFJHFZ9/ref=sr_1_1?crid=16DALFEDVT53F&dchild=1&keywords=1200w+server+power+supply&qid=1610902320&sprefix=server+1200w%2Caps%2C190&sr=8-1

with an adapter like

https://www.amazon.com/Ethereum-Mining-Breakout-Adapter-Graphics/dp/B07D6NC5LK/ref=sr_1_2?crid=3CKPJ9BQNK1EQ&dchild=1&keywords=server+psu+breakout+board&qid=1610902366&sprefix=server+psu+brea%2Caps%2C199&sr=8-2

And you will have a lot of 6 and 6+2 connectors and 1200ws added to your rig.