In order to make a reasonable guess about what the problem is we need to know more about the tank, the lights, the substrate, the fertilizing, the CO2 system, if any, etc. Any problems with plants can be caused by several things.
Ok so no, the leaves were not dry when the pic was taken. i took them out for the pic.
the tank is 330L tank
light: 6 bulbs of T5 39W
CO2: 4 bubbles\second
substrate: DIY, peat + humus coverd with graind Quarz
fertilizing: every sunday, teusday, thursday:
3.7 PPM of KNO3
0.65 PPM of KH2PO4
4.5 PPM of KCL
micro: plantex csm + b, 11 gram on 150 cc of water
dosing 1 cc per every day
Just a comment regarding your setup; you have a lot of light for your tank. You may want to check your CO2 levels (with a drop checker and a 4 dkH reference solution), as I think 4 bps in a 90g tank is quite low.
In addition, you may want to check your macronutrient levels with a calibrated test kit. Adding 3.7 ppm of KNO3 every other day may not be enough to meet the demands of your plants, considering you have ~2.6 WPG of T5 lighting...