problems with first hydro grow

Hey riu,
I am currently four weeks veg of my first hydro grow. Ive had numerous highly succesfull coco grows. This however is prooving to a bit of a challenge.

My system is as follows,
Pot in pot recirculating system, drains back to 60L res, top feed,
Feeding times of 15min on every six hours, nothing during lights out, so three feeds a day.
I have steady temps of night being 24.5c and day at 27.5c with 45-55% humidity,
Ag grow general hydro nutes,
100% perlite,
Ppm at approx 1300 ph ranging from 5.7-6.1 aiming for 5.8
600w hps cool tube, carbon sok and all that jazz,

So over the last two weeks my plants have steadily been looking worse for wear. The larger bottom shade leaves are yellowing, have small pin prick holes, and starting to taco downwards. This is only the bottoms doing this and not the tops.

I started first round of super cropping a few days ago. Was intending to start flowering one week from now.

Once flowering begins a second 600 cooltube will be added. This is in 6x6 tent.

So guys what im asking is, what do you possibly think this could be? Im really stumped and not to sure how to go about it. All four of my plants are showing these symptoms so im suspecting a nutrient problem. What do you guys think?

Sorry im unable to currently upload images

I'm no rocket scientist, and all my information is from learning through my own experiences and discussing things with people here on RIU, BUT 1300 ppm is waaaaaaay too high for a four week old plant. You never gave that baby a chance to veg properly you are just shocking it through life. Perlite as a hydro media is not sufficient because it does not retain water. Your plants roots are probably dehydrating in between cylcles and most definatley over night. Then you shock it with 1300 PPM. You probably could have still used coco for this style of hydro. Most people either use rockwool cubes or hydroton. Either will be better than perlite with your setup. There are general rules on hom much you should feed your plants in Hydro and at what stages. A quick search can provide you that info.

Hey mate, thanks for the reply.
I will definetly research ppm and adjust it as necessery. However i definetly feel that perlite is a substantial growing medium. I definetly retains more moisture than hydroton. It is a extremely porris? material. Im not underminning your opinion, but eother way im stuck sith it for the rest of this grow. Again i will look into different and better mediums.

What watering schedule would you reccomend to test atm. Unfortunatly due to the timers i have 15 min intervals are the minimum. I ll get a mpre precise one whe i can.

I tried a watering every hour but was getting clear signs of over watering within 24 hrs. What is it you reccomend as per tiimes?


Thanks for your input mate, its greatly appreciated.

What about air pumps? Lots of problems in systems like yours with areas where water will get stagnant and it sounds like you might have a root issue. What are res temps?

Ive got air pump in res already, though the piece in there is called an air curtain. Piece of shit really, the bubbles are quite small and steady so the water may be doing that. I will put in some better ones that will help stir it up a lot better. I dnt curently have a thermometer in there atm but id say the temps would be slightly cooler than the room , but i cant give a definate answer to that.

Set the intervals on ur timer as close together as possible if its gettin dehydrated. roots only absorb water for a less than a minute before they stop take up and its about 5 mins or so before they get hungry n feed again. however drooping leaves is usually caused by over watering. the spots u mentioned sound like an over abundance of nitrogen, nute burn. thats just off the top of my head tho. sorry if it doesnt help. good luck. btw KISS (Keep It Simple Silly<sorry that sounds weak but stupid sounds offensive as hell n im here to help ;cD>)

Thanks mate, u guys all have valid responses and ill take them all on. Ill do slight adjustments to determine what the issue is rather than all at once