yes the yellow gunk was on top and foaming , when there is bacteria in the solution you generally see things like that and the bottom feels slimy . You can aso get foaming from products that break the water tension just so you know . but the film you had along with the foam was screaming lean me out to me .
Yes plants grow extremely fast in hydro compared to soil they are night and day .
Training looks good , good job . now what i would be looking at is the ease of caring for them during flower after the stretch . depending on training and how long you let them grow before you initiate flowering decides that . Meanng if you let them get to large taking care of the ones in the center could be a bit of a chore . Always anticipate 1- 1 1/12 the stretch in height /diameter depending on your growing style .
You asked about feed . i am not familiar with the brand you are using . However for agruments sake lets say they are similar to other brands as far as strength and quality . Now me i am a low ppm style feeder . I do not go over 550 ppm on a 500 scale my entire grow and my plants will actually show signs of overfertilization if i do my system is quite efficient in nutrient delivery .
Now lets talk about yours and nutrient delivery yours is set to flood the pots and then drain them at specific times. The solution strength in that style system by following factory instructions is generally higher simply because of the time that solution is coming into contact with the roots . So look at it this way the less you flood the stronger your solution would need to be than if you flooded more often. Your medium does not hold nutrients it is merely there to help support the plant through the root structure . I feel that you would have greater success and less issues using less nutrients (about 1/2 strength) and flooding and draining twice as often then you would running full strength running a regular schedule . Why you ask? because you are moving twice as much oxygen through the pots as well as increasing the times that the plants can feed . If you do this and you start to see signs of deficiencies its easer to correct as all you need to do is increase the feed strength . Where as using a higher feed and starting to see signs of overfeeding/overfertaliztaion can truly be a pain in the rear to get under control . Less is more in alot of ways .
Now before you start thinking it will affect your yields . Understand this , every strain has a pre determined genetic amount it will produce . You are increasing feed times so you really aren't taking anything away . I produced over 5lbs from 6 plants in a 5x7 scrog never exceeding 550 ppm in my rdwc system and the yield exceeded the breeders range., i produced over 1/4 lb from one plant(3x3x6 tent,150w light) in coco(hempy style bucket) that was truly left to do it own thing only saturated and looked at once every 10 days ( not my style , but life was kicking my ass and i was very impressed with it living until the end let alone the yield) not going over 550 ppm the entire grow . Thats just some food for thought .
Now in regards to ph since you are using a controller you will have to monitor how much and how often its having tp correct ph . Me with having seen the slime i would not have it run for a couple days and adjust manually . Because if it fact it was and there is bacteria in your system watching ph at this stage of growth is a sure way to have a good idea as bacteria in hydro makes the ph drop , when i say drop i mean like easily past 5.5 down to the 4-5 range and fast . so you are running z7 .So lets say you do as suggested and see that your ph plummets ( not drift down ) after a day of feeding , it means you need a higher concentration z7 , hydroguard etc in your system to combat the bacteria . the res temp of 66 will aid in doing that in the res but you have to remember its flood and drain and the water left in the lines as well as the base of the modules is not being chilled and so that temp is alot higher and bacteria likes warmer places and the only time its getting the full strength of the z7 etc is when its being flooded. Thus increasing flood times and lowering nutrient strength also gives you the ability to combat what's in the lines/modules more effectivley .
here are a couple pics one of my shamefully neglected plant that i had spoken of and one of the last frow in my main room both never exceeding 550 ppm ...not that you asked but i use current culture nutrients ...i have used gh, and advanced nutes. I have to say i like current culture .
