Your PH should be between 5.3-5.9. So lower the PH of your nutrients to 5.3 or 5.4. until you get that run off to about 5.6. Also You are not giving them enough water to flush out the old salts and such, which is boosting your PH in the Coco. I had this same exact trouble once and did not notice it until I got the same splatches. But my PH of my run off was above 7.0. it took me about 3 days to get it down useing 4.5ish PH'd nutrients. I think you can do it with 5.3 PH. But remember, you have to have between 20-30% run off or the salts and crap will continue to build up. To help fix this I would have 40-50% run off for a day or two. And feed them at least once a day. I kid you not, you could feed them 6 times a day and not over water them. But you would eat through the nutrients and cost more money. The fewer waterings you do, the more run off you need. If you want to water them every other day, then boost to 50% run off. Once you get a handle on it, you can adjust this to your own way, and what the nutrients do. Not all nutrients react the same with in your coco.
Also, When I did research on that nutrient you were using. I only saw the one that was for Seedlings and cuttings. So if you are useing the one for vegging of plants, then do not go crazy on the amount you feed. But if you are useing the one for the seedlings and cuttings try and boost it higher, but very slowly over time. Just watch for the tips of your leafs to turn a light gold. then back off a little and give them a heavy watering. Like I said, I do not even use a PPM or EC pen anymore, they are useless once you can learn how to read the plants. Well, I guess they do have a place if you are useing a rez and want to top it off with water and nutrients. But I never do that even when running a recirculation system. I mix a fresh batch ever 7-10 days.
once ive fed mine how long do u think till they perk up ?