Help! Rockwool Problem.

I have a friend that is using a Ebb and Flow set-up with rockwool blocks. The blocks look very wet and have algae all over them. The plants look healthy but they are starting to get tiny yellow spots on the lower leaves. Does the algae have anything to do with the problem or is that a K deficency? I told them I thought it was a K problem and to flush first then use a complete NPK fertilizer and add a little exra K. Then get block covers but I dont know what the algae will do to the roots. Do you need to clean the blocks first? If so what do you use? Any help appreciated!

1. no nutes at this time, not neccessary that may be why theyre yellowing 2. alage is not good its from over wattering/ underwatering the rockwool, try flushing with plain 6.2 ph water and place something over your rockwool so algae cant photosynthesize therefore getting rid of the algae, ltr bro

algae isnt the hugest deal though, somepeople have no rpoblems, but i got a minor case or rot from it before