alright greenskeeper, i agree with both abefroman and whitebb, it appears to be overwatering with a slightly high nutrient concentration/inaccurate ph. I would cut back on your nutrients a bit, use only whats necessary and avoid extras as they are usually nothing but gimmicks. Ive been growing in coco for about 8 years now and ive personally come to love the dyna-gro line of nutes, use the "foliage-pro" for veg, and "bloom" for flowering, cal-mag will be the only other nutrient you really need but i also use dyna-gro's "pro-tekt" in my resevoir, its a silicon nute that helps protect the plant from environmental stress and just makes the plants much hardier. DEFINENTLY get a proper ph meter, you dont need a crazy expensive one, but you definitely need a meter, not strips, if youre gonna grow in coco, PH is important no matter what you grow in but coco can be particularly picky about it, as abeforman suggested 5.8-6.1 is the sweet spot for coco, but as long as your within the 5.5-6.2 range youll be fine, but strips are generally the most inaccurate way to check ph so do yourself a favor and just get a digital meter.
Idk much about your setup but ive found my preferred way to grow with coco is drip+drain to waste, flood and drain was good too but salt buildup can happen quickly if you go that way, youll obviously have to go through some trial and error to figure out what works best for you but drip+drain to waste gives me the best combination of total control and ease of use, youll probably go a few years before getting a nice professional setup going but DIY setups can be just as good, lookup "DIY drain to waste buckets" and see if it looks interesting to you, i love it because with drain to waste i just fill my reservoir once a week, twice a day my drip pump kicks on, i have it dialed in so each session of drip gives about 10% runoff, the runoff is tubed out the bottom of my pots to a small collection bucket that pumps it out the nearest window when the float switch is tripped. Your post mentions this is your first grow so im sure alot of this is confusing for you but dont be afraid to ask questions, lots of good info and helpful people on these boards. Good luck to ya!