whats happening to my plants

i think ive got swordtail plants, they were planted on monday in a substrate of washed pottingsoil under pool filter sand, ive added seachem fluorish excel as instructed on botle its a 60liter tank and theres 1 15W tube distributed by DARO, the leaves are becoming transparent in places and browning is also taking place, what could it be, maybe it needs some CO2 or what, the temp is 26 and PH 7.2.......... please help

im having trouble uploading pics

 

Most aquatic plants are grown out of water hydroponically. When they are submerged they have to change their physiology to adapt to submerged life. This essentially means they have to produce new submerged leaves the old leaves will dye back, and this is what is probably happening.
I wouldn't fertilize a new tank because there will be alot of nutrients in the system which won't be used by the plants until they are actually growing.
With Swords you can cut back quite a few leaves and cut the roots back drastically just a couple of centimeters is all you need. New roots will grow and new leaves too.