Newbie Grow, Pine Needles Pine Cones Ph Down help

My small plant wasn't growing after 5 days sprouted, it stayed at 4 inch but was green healthy. it is in beach sand(very fine from my pool) and some aquarium rocks about 40/60 sand/rocks. it still stays moist for over 2 days but i water it every 2 days anyways (i though i had to water multiple times a day in hydroponics, so let me know if i should wait longer to water)

I decided to start giving it very small amount of nutrient since it wasn't growing anymore, a combination of FloraNova grow 7-4-10, Natures Nectar Nitrogren 5-0-0 and few drops of B1 in 1L commercial water bottle. I definitely put less than recommended dose for seedlings in case to not hurt my baby. Now it is 8 days old and didn't grow much at all compared to 11 days sprouted soil grown of my friends (3x longer stem, could see 2nd set of real leaves mine only has first, and the first set of leaves is 4x the size of my baby). Did some research, and decided the most common problem might be PH was around 6.8+.

I want to reduce PH to see if it will grow better in the next week.

I have a pine tree and I want to use it as PH down, should I boil the needles/cones or just let them sit in room temp water?
I tried boiling some 5-6 pine cones, but it only brought down the ph of 500ML nutrient solution from 6.7-6.9 to around 6.3, so i guess it worked but i'll need a lot, especially when my baby grows up.

I'm going to try making it more concentrated but can something bad happen from using these? and would you boil it or just let it sit in water. Also, would the pine needle tea ruin my nutrient solution after a few days like regular drinking tea rots?

I'm a real newbie but I read a lot on forums. Every tip is appreciated.

Buy PH down (its cheap) or use lemon juice to be safe

Allright it seems the PH wasn't the problem. I just transplanted today because I had no idea why it wasn't growing past 5 inches (still only the first real leaves visible, and they are tiny)

When transplanting i realised, NO roots were able to escape the sponge the seeds started in (kinda like small rockwool cubes but a normal soft sponge instead). What happened was, since the sand from my pool was so fine and tiny (like, some pieces even less than 0.1 mm) the sand actually blocked all the small holes of the sponge and the sponge became hard only 2-3 tiny less than 1cm roots were able to come out of the sponge after 11 days!. I rinsed the sponge a lot so sand comes out and now I placed the sponge in bigger pot (6") with like 90% aquarium rocks and only kept a little sand for moisture.

This should work (i think) but probably will need more watering since there's less moisture now. I am manually watering atm.

I just hope it didn't get perma shocked for life although it is still green.