Northern Lights x Haze CLONE (NFT HYDRO)

Hello I am still disturbed by my plants, it's been two weeks since they do not grow too much... the leaves are light green with traces of burning or carances at the end of the leaves, I tried to put silicate in my water from GHE, no result, also increase my pump frequency which now turns on 15min per hour, I am currently at 1.1EC and my ec goes up every day in my tank by about 30 and my ph goes down every day too. my spider famer sf4000 is at 70cm at 60 percent the roots have started to stretch for some plants but I don't know what to do to make the leaves dark green again and strong sign of a vigorous growth! In all my hydro tanks it's the same problem since a long time !