Cloning with Super Thrive-Brown Roots?

My clones sit in 1" rockwool cubes in a clonning dome (one with the vents) and on top of a hydrofarm heating pad. I dipped them in FF:Bigbloom to begin with, and now I am spraying them daily with 1 drop of superthrive into one quarter gallon. 8 days until roots popped out the cubes, the problem is, the same day the roots popped out, they began to turn dark.. not good.

The dome sits near some seedlings (and a 6" fan) so the dome airs out a little quick since it's not completely air tight. I supplement this by spraying them 2-3 times a day. They dry out slightly, so I know I'm not overdoing the spray.

Anyone think the roots could be receiving too much heat? The tray is the type with holes, and it sits right on top of the heatpad. Inside the dome it's always 78F and like 85% humid.

What causes clones roots to start to turn brown? Anyone think I should discontinue the superthrive? Just use water for spray? Is one drop into a quarter gallon too much?

I'm not an expert but it sounds as if it's due to heat.. from my experience roots like to be more on the cool (not freezing of course) side than hot. The heat mat will increase temps to the root zone approximately 10+ degrees and to add to that most trays are black and are being bathed in sunlight so your root temps could be as high as 88+ degrees.. and if there's no oxygen to root zone (higher temps lower oxygen) then there will definitely be some discoloration.

Too much superthrive, try flushing for a week or two.. in the future... superthrive Calls for 1/4th teaspoon per gallon on the package... u ALWAYS take 1/4 or less of what the package says... so 1/8th tsp per gallon.. or less... typically go 1 Or 2.. drops per gallon... u gotta realize, superthrive is another form of a hormone enhancer, too much is the same as nuking ur plants hope this helps