Trust me it is the light getting in your tote . Algae does not take long to grow.
Even using Peroxide at 1 tsp per gallon will not kill it .. I have been there .. Your roots tell it all with the slime and probally smells like a Shit dirty mop too..
If you click my grow and go to the first post there and click the link for my set up .. you can see how much light was getting in my tub a rubberMaid 14 gallon ..
I started a grow and algae formed massive from light penetration in 2 days / I flushed it thinking with 1 stp per gallon was enough .
I then went to 3 tsp per gallon let it run for a for like 15 minutes then flushed it all out .. Needless to say algae was in there and messed me up big time My plants looked just like yours ,,
They did not pull through ... I was not happy ..
. I trashed 6 Easyryders fems ..
Make sure you are toatally light proof in the tub..
Make sure if you use a pump slow the flow to a drip to the rockwool also will help,,, not a flow and lots of air Bubbles the more bubbles the better LOL good luck..
I am on My second grow with that algae and light issue fixed now .. @nd time is a charm LOL Good luck