White Residue On Rockwool

Room specs-

7' x 10' room size.
3.5' x 5.5' 15 plant flowering "table".
15 plants, drain fill home made system. Watering once daily.
Plants in rockwool Hugos, suspended 3" off of the bottom of 5 gallon buckets cut down to 4 gallons.
Cutting edge solutions 3 part nutrients @ 60% strength. Flora organic enhancer w/ Humic Acid@ 50% strength.
250cfm exhaust, 300 cfm intake air conditioned.
Temps- daytime 75F @ 40% RH. nightime 67F @ 45% RH.
Lights- 600w HPS, 400w MH, 4 x 65w CFLs intra-canopy w/ custom built screens.
Started 12/12 on Feb 24th.

Everything is going great with this grow, but noticed something a little odd today. When I pulled the plastic off of one of my buckets to look at the rockwool cubes, there was a strange white mildew-like substance on the top of them. The white substance is on the top of every rockwool cube. Can anyone help me diagnose the cause of this? Pictures attached.

The pictures show slight nute burn @ the leaf tips. This is not recent, happened when I switched to flowering nutes (and trusted a newbie to filling my resevoir).

Pictures one and two show the discoloration I mentioned. The first one didn't focus very well, but you get the idea.

The last 3 pictures are not really relevant to the problem I'm having, but who doesn't like to look at bud pron?

Ouch looks like you got mold. I've had rockwool do that to me too. I wouldnt recommend rockwool for hydro only for clones going into dirt. Gotta make sure you cover it all the way with dirt too because that stuff stays moist forever

I've been using rockwool in this system for about 6 years now. Growing for about 12 years. I have seen just about everything that can happen, but i wanted a second opinion on what this is before I treat it. I usually keep my humidity low, so I have never had mold before. Also, there is no light getting to the rockwool cubes, none at all. That's why I wasn't sure it could be mold, doesn't mold need light to grow? And what is the most popular remedy for a mold problem?

There is a product called "plantacilin" its a all natural spray containing benificial bacteria's. I use it with good results. It will eat the mold

Its also safe to water your plants with 1/4 teaspoon a gallon. I use it in my promix a few times thruout my grow and also as a foliar spray if needed. Its all natural organic

Right on, thanks for the tip Willie. Heading down to the shop right now to grab some. I'll post in a week or so with my results so anyone with a similar problem will see if it works.

Turns out it wasn't mold or anything growing at all. My DI tank was done for, I was getting lime buildup on my rockwool blocks and my poly tubing.

10 Percent solution of Lemon Joy dish soap works great. Spray a little right on top of the cube. Will come back eventually but takes care of it safely and chemical free. Stops it from working its way through the cube