New growth looks brown

pigmentation.. might get some colorful leaves or it might grow out of it never to be seen again. this is not anything bad. If night time temps are below 68F, that could cause a faint red like this to show up. So, either genetics or temperatures.. neither is a huge concern but should try to stay 68F or above when lights go out. This is same effect that causes fall colors (the cold part). --- Do continue to fertilize as you have. Ceasing will only slow your plant down. Do react to leaf symptoms and adjust, of course. If anything else is going on concurrently to what you ahve pictured here.

Hello my friend, this is because of the nutrients. You do not need to top dress or use other additives for the next 2 weeks. Happy new year my friend and enjoy this grow!

was the soil amended already and how high are your lights up and a full picture of the plant as well would help alot more ...we need to hear more about your environment

Might be from the light or the PH is my guess. ....[][][].... Gaia Green "GG" is good but only needs topdressing every 4 weeks and as a seedling this should happen when its getting transplanted to a bigger pot at about 3-4 weeks in age. When you adding in rock dust it is going to raise the PH over time as its a lot of calcium carbonate and other minerals. The fish shit IDK about I have not used it in combination with GG, GG has almost everything it needs, I find it need a bit more Mg then it provides and could use a boost in K but is not 100% needed. ....[][][].... Give it a bit more time and try to keep the PH stable with all the rock dusts being added in. Also give them a transplant soon as they will need it and see how it progresses. It also helps to mix in GG AP 4-4-4 with GG PB 2-8-4 so the nitrogen is not to high. I notice it will get mild N tox when just using 4-4-4 on its own. a 50/50 mix would yield 3-6-4 and and a 75/25 mix would yeild 3.5-5-4 a bit better ratio for veg but not a massive difference. Top Dress 15ml per 4L of substrate, Fortify mix with 45ml per 4L of substrate for transplants, do not top dress till 3-4 weeks have passed. ....[][][].... Good Luck!