Hi:

My tonina are started to show brown tips. Any clue on this ?

water parameters :

PH 6.6
KH 8dkh
CO2 (using the calculator is around 50 + ppm) using external reactor
lighting 10 hrs , 2 x 150w MH , 1pm to 11pm.
Tank facing 20' away from window. Sometime early morning sun shines on small corner of the tank . Not the centre part of the tank.
tank 6x2x2
dosing : LushGro-Aqua (50ml) after water change 50%, every 2 days after, ie Friday, Monday, Wednesday
NO3 10ppm (using APP kit)
Ca/Mg - 1 bag of small coral chips inside carnister

Questions :
1) Is the coral chip distort my reading on PH,dKH ?
2) If the NO3 at 10ppm, should I dose K2PO4 (1ppm) every dosing of LushGrow-Aqua ?
3) Through observation, tonina does not bubble , after I dosed K2PO4 and LushGrow-Micro. Which are the nutrient trigger this ? Is the bubbling give indication of missing nutrient added in ?
4) Water seems clear from the front side glass, but look from both left or right hand side, the water is not as clear. Is this normal ?
5) No algae spotted on plants, except the front side glass . Can see small particles from the side view. Almost the whole front glass. Is this because of nutrient issue or the lighting is too long.

Thanks in advance.