Need advise with issue

First off, welcome!

That’s a painfully expensive 288 watt rig.

I can only theorize a few things:
Mold/algae/bad nasties happen in hydro when water temps get too high and/or light leaks happen. What’s the temp of the water in your reservoir?

Can you take a pic of the plants without the blurple lights on? Natural light is best to be able to see what’s happening on the plant itself.

Are you measuring your PH and PPMs in the reservoir? If so, what are those numbers?

It very easily is partly (if not entirely) insufficient lighting for three plants.

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